feat: DEPR USE-JWT-COOKIE header (#35393)

This repo is no longer using USE-JWT-COOKIE header,
since it has the required edx-drf-extensions>10.2.0,
where it was fully removed.

This is final clean-up for this repo.

See "[DEPR]: USE-JWT-COOKIE header" for more details:
- https://github.com/openedx/edx-drf-extensions/issues/371

cms/envs/common.py

@@ -2544,7 +2544,6 @@ if FEATURES.get('ENABLE_CORS_HEADERS'):
 # because that decision might happen in a later config file. (The headers to
 # allow is an application logic, and not site policy.)
 CORS_ALLOW_HEADERS = corsheaders_default_headers + (
-    'use-jwt-cookie',
     'content-range',
     'content-disposition',
 )