test(e2e): update assertion for sanitized inference error message (SEC-008)

The SEC-008 fix changed the error message from 'no compatible route
for source protocol ...' to 'no compatible inference route available'.
Update the E2E assertion substring to match.

Author: johntmyers

e2e/python/test_inference_routing.py

@@ -319,7 +319,7 @@ def call_anthropic_messages() -> str:
         assert result.exit_code == 0, f"stderr: {result.stderr}"
         output = result.stdout.strip()
         assert output.startswith("http_error_400"), output
-        assert "no compatible route" in output
+        assert "no compatible inference route" in output
 
 
 def test_non_inference_host_is_not_intercepted(