add TODO to remove unnecessary logic

tools/interop_matrix/run_interop_matrix_tests.py

@@ -116,6 +116,10 @@ def find_all_images_for_lang(lang):
             return {}
         releases = [args.release]
 
+    # TODO(jtattermusch): why do we need to query the existing images/tags?
+    # From LANG_RUNTIME_MATRIX and LANG_RELEASE_MATRIX it should be obvious
+    # which tags we want to test - and it should be an error if they are
+    # missing.
     # Images tuples keyed by runtime.
     images = {}
     for runtime in client_matrix.LANG_RUNTIME_MATRIX[lang]: