Remove UserMenu component render modifier

[michaelchadwick]

Refs ilios/ilios#5374

Also fixed a bug where if you keyboard tabbed over to the user menu and pressed UpArrow, it would throw a console error: Uncaught TypeError: Cannot read properties of undefined (reading 'previousElementSibling')

[michaelchadwick]

Added keyboard navigation testing to UserMenu component. Needed to add a slight delay in both the component and integration test to properly set focus and test for it.

[jrjohnson]

I think there needs to be another check on item?

[sentry-io]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ TypeError: Cannot read properties of null (reading 'focus') route:dashboard.calendar View Issue

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