[stable34] chore: Reduce PHPUnit test matrix on stable34 and remove coverage

[come-nc]

Summary

Only keep min and max version for PHP and DB engines on stable branches.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[come-nc]

This is a good start, let’s merge. I’ll most likely open a follow-up to remove more coverage on stable34, and when backporting to stable33 I’ll try to do both PRs at once.

[come-nc]

/backport to stable33