Avoid false positive for '1st'

What does this MR do and why?

The vale rule that asks for a space between 1 and s (to mean "1 second") is showing a false positive in this file. The text reads 1st April.

This MR updates the regex to make an exception for 1s if there is a "t" after the "s".

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Check out this branch
2. Run Vale against a file that previously had false positives: vale --config .vale.ini doc/ci/pipelines/cicd_minutes.md
3. You should not get a gitlab.Units warning.
4. Edit cicd_minutes.md and add something that should warn (e.g, 1s)
5. Run the check again: vale --config .vale.ini doc/ci/pipelines/cicd_minutes.md
6. This time, you should get a gitlab.Units warning.

MR acceptance checklist

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