[tests] Increase timeouts for linkcheck build tests.

[jayaddison]

Feature or Bugfix

• Workaround

Purpose

• Reduce distration due to failed continuous integration pipelines.

Detail

• Increase the timeout duration in linkcheck-related test roots by a factor of 5x, to a quarter-second.

Relates

• May resolve tests/test_builders/test_build_linkcheck.py::test_defaults flaky for docutils HEAD CI #12159.

[chrisjsewell]

Cheers. Well the tests are at least passing in this instance, so thats a good start. If it stops the issue with the flaky test failure, then pragmatically I think its a good idea, and we can bear in mind fixing the root cause at a later date

[jayaddison]

Thanks @chrisjsewell - and yep, exactly - hopefully an improvement even if not a complete fix.