Update test for altered Notebook deprecation warning

Author: maresb

base-notebook/test/test_start_container.py

@@ -33,7 +33,7 @@ def test_start_notebook(container, http_client, env, expected_server):
     ), f"Not the expected command (jupyter {expected_server}) was launched"
     # Checking warning messages
     if not env:
-        msg = "WARN: Jupyter Notebook deprecation notice"
+        msg = "WARNING: Jupyter Notebook deprecation notice"
         assert msg in logs, f"Expected warning message {msg} not printed"