Bug 1991819 - Fix failing extensions related UI tests r=aaronmt

This should fix the following UI tests:

verifyTheExtensionsMenuListAfterRemovingAnExtensionTest
verifyTheExtensionMenuListWhileExtensionsAreDisabledTest
verifyTheExtensionInstallationTest
In all 3 cases the main menu button displayed "No extension enabled" after installing some of the recommended extensions.
After taking a closer look, I've noticed that the name of certain extensions isn't displayed in the main menu after installation.

To overcome this inconsistency, I've removed those extensions from our list, and added a retry loop to install a recommended extension (this is needed in case all 3 recommended extensions that are being displayed in the main menu are those that don't get their name displayed after installation)

All 3 UI tests successfully passed 50x on Firebase ✅

Differential Revision: https://phabricator.services.mozilla.com/D268382