Make lint job block merges

[JelleZijlstra]

Bug report

Bug description:

#149276 was merged despite a failing lint check, making all later PRs also fail. Let's prevent that by incorporating lint into the "All required checks pass" check.

CPython versions tested on:

3.14

Operating systems tested on:

No response

Linked PRs

• gh-149289: Make lint failures block merge #149290

[JelleZijlstra]

Fixed by Hugo in config.