feat(nav): Replace top menu term with top bar

What does this MR do?

The top menu is supposed to be referenced as the top bar per the style guide. This helps reduce the terms people use to refer to this element in GitLab.

Does this MR meet the acceptance criteria?

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• The “What does this MR do?” section in the MR description is filled out, explaining the reasons for and scope of the proposed changes, per “Say why not just what”.
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