fix: narrow vendor_collections_dir fixture teardown scope

Only remove the collection directory the fixture created
(redhat/indirect_accounting) instead of the entire
/var/lib/awx/vendor_collections/ root, so we don't accidentally
delete vendor collections that may have been installed by the
build process.

Forward-port of ansible/tower#7350.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

awx/main/tests/live/tests/test_indirect_counting_external_queries.py

@@ -111,8 +111,8 @@ def vendor_collections_dir():
 
     yield base
 
-    # Cleanup
-    shutil.rmtree(VENDOR_COLLECTIONS_BASE, ignore_errors=True)
+    # Cleanup: only remove the collection we created, not the entire vendor root
+    shutil.rmtree(base, ignore_errors=True)
 
 
 @pytest.fixture(autouse=True)