Resolve "Performance issue: 502 errors on rendering of issues with heavy markdown contents"

What does this MR do?

This helper is used for extracting part of the issue / MR / whatever description for use in the description meta tag:

1. To do that, we look at the source of the Markdown description.
2. We then strip out all HTML tags.
3. And then take the first 30 words.

Doing that can be really slow - especially as Markdown is supposed to be treated as plain text. There are many better ways to do this, but the immediate performance fix is to swap steps 2 and 3. This does mean that the description may be less than 30 words (or even empty), but it is much faster when the description is very long.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

Closes #62116 (closed).