exclude 7.2 and 7.3 checks against trunk

[masteradhoc]

Fixes #766

What?

Adjust the GitHub Actions PHP/WP test matrix to skip unsupported PHP versions when testing against WordPress trunk.

Why?

WordPress trunk no longer supports PHP 7.2 and 7.3. Running CI jobs for these combinations produces expected failures and unnecessary noise while still providing no additional coverage.

How?

Use GitHub Actions’ matrix.exclude feature to remove only the PHP 7.2/7.3 + WP trunk combinations, while keeping those PHP versions tested against released WordPress versions (e.g. latest, 6.8).

This follows the official GitHub Actions matrix exclusion mechanism:
https://docs.github.com/en/actions/using-jobs/using-a-matrix-for-your-jobs#excluding-matrix-configurations

Testing Instructions

Open the GitHub Actions run for this PR.

Verify that:

• Jobs do not run for PHP 7.2 or PHP 7.3 with WP trunk.
• Jobs do run for PHP 7.2 and PHP 7.3 with released WordPress versions.

Confirm that all remaining matrix jobs pass as expected.

Screenshots or screencast

Changelog Entry

Changed – CI test matrix to skip unsupported PHP versions for WordPress trunk.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: masteradhoc <masteradhoc@git.wordpress.org>
Co-authored-by: kasparsd <kasparsd@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[kasparsd]

This is great!

Could you please fix the merge conflict?

[masteradhoc]

@kasparsd fixed :) thanks for the very fast review!!