fix(header): header opacity properly resets on collapsible titles

[liamdebeasi]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

On non-scrollable pages (I.e. pages that do not scroll but still have the rubber band effect), the opacity on the collapsible titles does not reset properly

What is the new behavior?

Opacity resets properly (added a 1px buffer -- I think this is mostly a safari quirk/rounding quirk)

Does this introduce a breaking change?

• Yes
• No

Other information