Previously, _authenticate_tenant only skipped extension auth for
internal requests when _current_schema was set to a non-public schema.
This caused async HTTP retain (document upload with async_processing=True)
to fail with AuthenticationError because the worker had no API key and
the schema was "public".
Remove the public-schema guard since internal tasks were already
authenticated at submission time. The worker sets _current_schema from
the task's _schema field for tenant schemas, and it defaults to "public"
for public schema tasks — both are valid.
d57e8639c5