Clicking on the opened track selector button should close it

Click on the track selector "X/Y tracks :small_red_triangle_down:" button to open it.
Click again.

Expected: The list of tracks should get closed.

Actual: The list blinks out for a fraction of a second, and comes back.
The only way to close it is to click "Show all tracks", or click somewhere outside the list (hoping not to trigger any unwanted action).

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-494)