refactor!: remove redundant ENABLE_COURSEWARE_MICROFRONTEND toggle (#26792)

The Django setting
FEATURES['ENABLE_COURSEWARE_MICROFRONTEND']
has been an additional gate to activating
usage of the Learning MFE for an Open edX
instance.

The toggle is redundant with the
`courseware.courseware_mfe`
Waffle flag. By removing it, we simplify our config
and simplify our path towards making the Learning MFE
the default courseware experience.

TNL-7796

openedx/core/djangoapps/courseware_api/views.py

@@ -89,20 +89,14 @@ class CoursewareMeta:
         This method is the "opposite" of _redirect_to_learning_mfe in
         lms/djangoapps/courseware/views/index.py. But not exactly...
 
-        1. It needs to respect the global
-           ENABLE_COURSEWARE_MICROFRONTEND feature flag and redirect users
-           out of the MFE experience if it's turned off.
-        2. It needs to redirect for old Mongo courses.
-        3. It does NOT need to worry about exams - the MFE will handle
+        1. It needs to redirect for old Mongo courses.
+        2. It does NOT need to worry about exams - the MFE will handle
            those on its own. As of this writing, it will redirect back to
            the LMS experience, but that may change soon.
-        4. Finally, it needs to redirect users who are bucketed out of
+        3. Finally, it needs to redirect users who are bucketed out of
            the MFE experience, but who aren't staff. Staff are allowed to
            stay.
         """
-        # REDIRECT: feature disabled globally
-        if not settings.FEATURES.get('ENABLE_COURSEWARE_MICROFRONTEND'):
-            return False
         # REDIRECT: Old Mongo courses, until removed from platform
         if self.course_key.deprecated:
             return False