chore(python): exclude path in renovate.json [autoapprove] (#1549)

chore(python): exclude path .kokoro/requirements.txt in renovate.json

synthtool/gcp/templates/python_library/renovate.json

@@ -5,7 +5,7 @@
     ":preserveSemverRanges",
     ":disableDependencyDashboard"
   ],
-  "ignorePaths": [".pre-commit-config.yaml"],
+  "ignorePaths": [".pre-commit-config.yaml", ".kokoro/requirements.txt"],
   "pip_requirements": {
     "fileMatch": ["requirements-test.txt", "samples/[\\S/]*constraints.txt", "samples/[\\S/]*constraints-test.txt"]
   }