chore: Update gapic-generator-python to v1.13.0

Google APIs · copybara-github · commit 44582d0577fd · 2023-11-29T14:50:32.000-08:00
PiperOrigin-RevId: 586460538
diff --git a/WORKSPACE b/WORKSPACE
@@ -322,7 +322,7 @@ load("@rules_gapic//python:py_gapic_repositories.bzl", "py_gapic_repositories")
 
 py_gapic_repositories()
 
-_gapic_generator_python_version = "1.12.0"
+_gapic_generator_python_version = "1.13.0"
 
 http_archive(
     name = "gapic_generator_python",
