Remove inline "position:sticky" from "header".

[jaredasutton]

Why:

Using "position:sticky" on both the component root element and the header element causes the header element to move down the page as the user scrolls down.

What's being changed:

Only the component root element will have "position:sticky."

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• I have reviewed my changes in staging (look for "Automatically generated comment" and click Modified to view your latest changes).
• For content changes, I have completed the self-review checklist.

Writer impact (This section is for GitHub staff members only):

• This pull request impacts the contribution experience
  • I have added the 'writer impact' label
  • I have added a description and/or a video demo of the changes below (e.g. a "before and after video")

[welcome]

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[gracepark]

Hey @jaredasutton thanks for submitting this! What timing - we have a PR that's being merged now to fix this! I'll close this for now. If you don't see the update in the next hour or so, please reopen!