Removes bold styling for header-text-inner class, used in collapsibles

[clreaume]

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

[jhgilbert]

[Automated message] This PR has merge conflicts created by the docs repo reorg project. Because this PR is marked as a work in progress, no attempt was made to auto-resolve the conflicts. When your PR is finished, you can queue your PR for an auto-fix by removing the WORK IN PROGRESS label and the astro-reorg-skip label. Your PR will be processed in the next batch of attempted auto-fixes.

This is an automated comment, but if you have a question, you can mention me in this PR (external contributors) or reach out in #docs-repo-reorg-support on Slack (internal contributors).

[jhgilbert]

[Automated message] This PR has merge conflicts caused by the recent docs repo reorg (files moved from the repo root into hugo/). A new PR with your commits translated to the correct paths has been opened: #39072

Please follow the instructions in the PR description.

This is an automated comment, but if you have a question, you can mention me in this PR (external contributors) or reach out in #docs-repo-reorg-support on Slack (internal contributors).