Bump minimum required WP to 6.3 #11503

Job	Run time
Pre run	3s
Lint: CSS	16s
E2E test: JS (1, 2)	4m 24s
Build: ${{ matrix.build }} build ZIP	0s
E2E test: JS (2, 2)	5m 57s
Feature tests: PHP 7.4, WP latest	1m 52s
Feature tests: PHP 8.3, WP trunk	1m 53s
Lint: JS	29s
Feature tests: PHP 8.2, WP trunk	2m 1s
Lint: PHP	44s
Static Analysis: PHP	52s
Feature tests: PHP 8.1, WP trunk	1m 59s
Feature tests: PHP 8.0, WP latest	1m 45s
Unit test: JS	43s
Feature tests: PHP 7.4, WP 6.3	1m 44s
Unit test: PHP 8.0, WP latest	2m 1s
Unit test: PHP 8.3, WP trunk	2m 28s
Unit test: PHP 8.2, WP trunk	2m 2s
Unit test: PHP 8.1, WP trunk	2m 3s
Unit test: PHP 8.0, WP trunk	2m 35s
Unit test (with coverage): PHP 8.0, WP latest	4m 16s
Unit test: PHP 8.0, WP latest	1m 26s
Unit test: PHP 7.4, WP latest	1m 58s
Unit test: PHP 7.4, WP latest	1m 32s
Unit test: PHP 7.4, WP 6.3	2m 18s
Unit test: PHP 7.4, WP 6.3	1m 34s
Upload plugin ZIPs to Google Cloud Storage	0s
Comment on PR with links to plugin ZIPs	0s
	48m 55s

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