ref: remove unused rest framework JSONField (#96955)

use the rest framework one instead

<!-- Describe your PR here. -->

Author: asottile-sentry

src/sentry/api/serializers/rest_framework/__init__.py

@@ -3,7 +3,6 @@
 from .dashboard import *  # noqa: F401,F403
 from .environment import *  # noqa: F401,F403
 from .group_notes import *  # noqa: F401,F403
-from .json import *  # noqa: F401,F403
 from .list import *  # noqa: F401,F403
 from .origin import *  # noqa: F401,F403
 from .project import *  # noqa: F401,F403