Add help module dependency requirement for firebase.help route

It looks like the above commit is not enough to fix the issue. Accessing the firebase.configuration route throws the following exception:

Uncaught PHP Exception Symfony\Component\Routing\Exception\RouteNotFoundException: "Route "firebase.help" does not exist." at /var/www/html/docroot/core/lib/Drupal/Core/Routing/RouteProvider.php line 206

The issue lies in the firebase.help local task, which remains defined if the help module is uninstalled and references the non-existing route firebase.help.

Fixed issue by providing a derivative to generate the help local task dynamically, only if the help module is enabled.