patch test_inventory_update_injected_content

* proot now enabled at task-level
  since tasks are no longer calling
  awx-manage (which would set up its own proot)
* dropping proot env var since it's not
  relevant to the test

awx/main/tests/functional/test_inventory_source_injectors.py

@@ -216,6 +216,7 @@ def test_inventory_update_injected_content(this_kind, inventory, fake_credential
         env.pop('ANSIBLE_COLLECTIONS_PATHS', None)  # collection paths not relevant to this test
         env.pop('PYTHONPATH')
         env.pop('VIRTUAL_ENV')
+        env.pop('PROOT_TMP_DIR')
         base_dir = os.path.join(DATA, 'plugins')
         if not os.path.exists(base_dir):
             os.mkdir(base_dir)