Add workaround for excessive whitespace in MediaWiki excerpts (fixes #2259)

[SnoopJ]

Description

This PR coalesces repeated whitespace in MediaWiki excerpts (#2259)

Checklist

• I have read CONTRIBUTING.md
• I can and do license this contribution under the EFLv2
• No issues are reported by make qa (runs make quality and make test)
  • NOTE: I do see 9 test failures, 72 errors, but this is the same result against the current HEAD (984e1b9)
• I have tested the functionality of the things this change touches

[dgw]

Already approved by multiple devs in #2259 discussion and on IRC.

• NOTE: I do see 9 test failures, 72 errors, but this is the same result against the current HEAD (984e1b9)

You didn't specify anything about your dev environment, but it sounds like some things are probably missing. My local copy of HEAD passes all tests, and this patch passed in CI.

[SnoopJ]

Yep, goofed up and didn't pay attention to the dev requirements. Passing now with the stuff I was missing.