Move edit button out of heading elements

[colleenmcginnis]

Closes #1966

This PR moves the edit button out of the heading elements in the body of the content (edit buttons were already added outside page titles in #3015). This is important because when the edit button is inside the heading element, technically the full text of the heading includes edit appended to the end of the intended heading text. This is getting picked up by Google, but may also cause unexpected results elsewhere including for users using screenreaders.

Note: I opted for updating the HTML and using Bootstrap CSS classes to avoid having to bump the name (-v1 to -v2) of the CSS file. If the user gets the updated HTML with a cached version of the CSS and JavaScript files, the edit button should still be positioned correctly and work as expected.

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[bmorelli25]

Wow. You can even copy/paste headings now without the "edit" getting in the way!