chore(deps): update dependency google-cloud-private-ca to v1.13.1 (#12900)

Co-authored-by: Katie McLaughlin <[email protected]>

Author: renovate-bot

privateca/snippets/requirements.txt

@@ -1,2 +1,2 @@
-google-cloud-private-ca==1.8.0
-google-cloud-monitoring==2.23.1
+google-cloud-private-ca==1.13.1
+google-cloud-monitoring==2.23.1