The sidebar and secondary toolbar both have a reference to their toggle
buttons in their own sections in `getViewerConfiguration`, so it makes
sense for the findbar to do the same.
While we actually have a findbar-specific reference to the toggle
button, I noticed that we don't use it consistently because the toolbar
also has a reference to the exact same toggle button and we use both in
the code. This is probably for historical reasons: the docstring in the
toolbar file indicates that the `viewFind` element is an input to the
component, but that option is never actually used in the code itself.
This commit fixes the issue by removing the toolbar-specific reference,
since it's not actually used (anymore) in the toolbar code, so that we
consistently use the findbar-specific reference everywhere.
f430a6bfd4