Update python Docker tag to v3.13

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
python	final	minor	3.12-slim -> 3.13-slim

---

Configuration

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[github-actions]

license-eye has checked 99 files.

Valid	Invalid	Ignored	Fixed
0	60	39	0

Click to see the invalid file list

• Dockerfile
• action.yaml
• generate-src-docs.sh
• main.py
• src/gatekeeper/init.py
• src/gatekeeper/action.py
• src/gatekeeper/check.py
• src/gatekeeper/clients.py
• src/gatekeeper/commit.py
• src/gatekeeper/constants.py
• src/gatekeeper/content.py
• src/gatekeeper/discourse.py
• src/gatekeeper/docs_directory.py
• src/gatekeeper/download.py
• src/gatekeeper/exceptions.py
• src/gatekeeper/index.py
• src/gatekeeper/metadata.py
• src/gatekeeper/migration.py
• src/gatekeeper/navigation_table.py
• src/gatekeeper/reconcile.py
• src/gatekeeper/repository.py
• src/gatekeeper/sort.py
• src/gatekeeper/types_.py
• tests/init.py
• tests/conftest.py
• tests/factories.py
• tests/integration/init.py
• tests/integration/conftest.py
• tests/integration/test___init__run_conflict.py
• tests/integration/test___init__run_migrate.py
• tests/integration/test___init__run_reconcile.py
• tests/integration/test_discourse.py
• tests/integration/types.py
• tests/types.py
• tests/unit/init.py
• tests/unit/action/init.py
• tests/unit/action/test_other_actions.py
• tests/unit/action/test_update_action.py
• tests/unit/conftest.py
• tests/unit/helpers.py
• tests/unit/test___init__.py
• tests/unit/test_check.py
• tests/unit/test_commit.py
• tests/unit/test_content.py
• tests/unit/test_discourse.py
• tests/unit/test_docs_directory.py
• tests/unit/test_download.py
• tests/unit/test_index.py
• tests/unit/test_index_contents_get.py
• tests/unit/test_index_contents_hierarchy.py
• tests/unit/test_index_contents_parse.py
• tests/unit/test_metadata.py
• tests/unit/test_migration/init.py
• tests/unit/test_migration/test_private.py
• tests/unit/test_migration/test_public.py
• tests/unit/test_navigation_table.py
• tests/unit/test_reconcile.py
• tests/unit/test_repository.py
• tests/unit/test_sort.py
• tests/unit/test_types_.py

Use this command to fix any missing license headers

```bash

docker run -it --rm -v $(pwd):/github/workspace apache/skywalking-eyes header fix

</details>

[github-actions]

Suggested change

	# Copyright 2024 Canonical Ltd.
	# Copyright 2025 Canonical Ltd.
	# See LICENSE file for licensing details.
	# Copyright 2024 Canonical Ltd.

[github-actions]

Lint checks failed for 1ae69d5

```

/home/ubuntu/actions-runner/_work/discourse-gatekeeper/discourse-gatekeeper/src/gatekeeper/check.py:171: supppressed ==> suppressed
/home/ubuntu/actions-runner/_work/discourse-gatekeeper/discourse-gatekeeper/src-docs/check.py.md:54: supppressed ==> suppressed

[github-actions]

Test coverage for 1ae69d5

Name                                 Stmts   Miss Branch BrPart  Cover   Missing
--------------------------------------------------------------------------------
src/gatekeeper/__init__.py              96      0     34      0   100%
src/gatekeeper/action.py               158      0     44      0   100%
src/gatekeeper/check.py                 62      0     16      0   100%
src/gatekeeper/clients.py               11      0      0      0   100%
src/gatekeeper/commit.py                41      0     12      0   100%
src/gatekeeper/constants.py              8      0      0      0   100%
src/gatekeeper/content.py               49      0      8      0   100%
src/gatekeeper/discourse.py            157      0     32      0   100%
src/gatekeeper/docs_directory.py        32      0      2      0   100%
src/gatekeeper/download.py              21      0      2      0   100%
src/gatekeeper/exceptions.py            14      0      0      0   100%
src/gatekeeper/index.py                141      0     52      0   100%
src/gatekeeper/metadata.py              58      0     28      0   100%
src/gatekeeper/migration.py            101      0     28      0   100%
src/gatekeeper/navigation_table.py      64      0     18      0   100%
src/gatekeeper/reconcile.py            122      0     46      0   100%
src/gatekeeper/repository.py           292      0     54      0   100%
src/gatekeeper/sort.py                  42      0     10      0   100%
src/gatekeeper/types_.py               201      0      8      0   100%
--------------------------------------------------------------------------------
TOTAL                                 1670      0    394      0   100%

Static code analysis report

Working... ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 0:00:03
Run started:2025-01-24 11:38:01.730017

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 17878
  Total lines skipped (#nosec): 3
  Total potential issues skipped due to specifically being disabled (e.g., #nosec BXXX): 0

Run metrics:
  Total issues (by severity):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
  Total issues (by confidence):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
Files skipped (0):