chore(deps): update dependency tensorflow to v2.7.2 [security] (#8329)

Author: renovate-bot

ml_engine/online_prediction/requirements.txt

@@ -1,5 +1,5 @@
 tensorflow==2.8.1; python_version > "3.6"
-tensorflow==2.6.4; python_version < "3.7"
+tensorflow==2.7.2; python_version < "3.7"
 google-api-python-client==2.47.0
 google-auth==2.6.2
 google-auth-httplib2==0.1.0