Removes an obsolete Django setting, ALLOW_ALL_ADVANCED_COMPONENTS.

We moved from configuring installed components in settings.py files to using just Python entry points.
This used to be a setting which enabled all XBlocks with appropriate entry points.
It was removed from the rest of the codebase in a previous PR, and this usage was
inadvertently left behind.

cms/envs/bok_choy.env.json

@@ -73,7 +73,6 @@
         "ENTRANCE_EXAMS": true,
         "MILESTONES_APP": true,
         "PREVIEW_LMS_BASE": "preview.localhost:8003",
-        "ALLOW_ALL_ADVANCED_COMPONENTS": true,
         "ENABLE_CONTENT_LIBRARIES": true,
         "ENABLE_SPECIAL_EXAMS": true,
         "SHOW_LANGUAGE_SELECTOR": true,