[reorg fix] Removes bold styling for header-text-inner class, used in collapsibles

[jhgilbert]

🤖 Auto-generated fix for #38408.

@clreaume — the docs repo reorg created merge conflicts in your PR #38408. This is an auto-generated replacement with the file paths fixed; please use it instead of the original.

This PR replays the commits from #38408 with file paths translated to the post-reorg hugo/ layout. The original commits are preserved — same messages and authorship.

The original PR (#38408) will be closed in favor of this one.

Next steps:

1. Verify that this PR looks correct in the browser.
2. Remove the WORK IN PROGRESS label from this PR.
3. Wait for the standard docs team approval before merging. Optionally, you can check the 'ready for merge' checkbox below if you would like the docs team to merge it for you.

• Ready for merge

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Original PR description:

What does this PR do? What is the motivation?

Removes bolding from the CSS class used to style collapsible titles, so headers display consistently!

Merge readiness

Not ready; want to get feedback from docs team first

• Ready for merge

AI assistance

Used Claude to investigate impact

Additional notes

n/a