use lower case stack names for pull requests (#172)

## Summary

- Routine Change

### Details

Use lowercase stack names for pull requests

## Reviews Required

**Check who should review this. Remove this line once this has been
done**

- [x] Dev
- [ ] Test
- [ ] Tech Author
- [ ] Product Owner

## Review Checklist

:information_source: This section is to be filled in by the
**reviewer**.

- [x] I have reviewed the changes in this PR and they fill all or part
of the acceptance criteria of the ticket, and the code is in a mergeable
state.
- [x] If there were infrastructure, operational, or build changes, I
have made sure there is sufficient evidence that the changes will work.
- [ ] I have ensured the jira ticket has been updated with the github
pull request link

.github/workflows/pull_request.yml

@@ -58,7 +58,7 @@ jobs:
     needs: [get_issue_number, package_code, get_commit_id]
     uses: ./.github/workflows/sam_release_code.yml
     with:
-      STACK_NAME: PR-${{needs.get_issue_number.outputs.issue_number}}
+      STACK_NAME: pr-${{needs.get_issue_number.outputs.issue_number}}
       ARTIFACT_BUCKET_PREFIX: PR-${{needs.get_issue_number.outputs.issue_number}}
       TARGET_ENVIRONMENT: dev-pr
       ENABLE_MUTUAL_TLS: false
@@ -78,7 +78,7 @@ jobs:
     needs: [get_issue_number, package_code, get_commit_id]
     uses: ./.github/workflows/sam_release_code.yml
     with:
-      STACK_NAME: PR-sandbox-${{needs.get_issue_number.outputs.issue_number}}
+      STACK_NAME: pr-sandbox-${{needs.get_issue_number.outputs.issue_number}}
       ARTIFACT_BUCKET_PREFIX: PR-sandbox-${{needs.get_issue_number.outputs.issue_number}}
       TARGET_ENVIRONMENT: dev-pr
       ENABLE_MUTUAL_TLS: false