chore: use gapic-generator-python 0.58.4

Google APIs · copybara-github · commit 73da6697f598 · 2021-12-30T17:41:17.000-08:00
fix: provide appropriate mock values for message body fields

committer: dovs
PiperOrigin-RevId: 419025932
diff --git a/WORKSPACE b/WORKSPACE
@@ -232,7 +232,7 @@ load("@rules_python//python:pip.bzl", "pip_repositories")
 
 pip_repositories()
 
-_gapic_generator_python_version = "0.58.1"
+_gapic_generator_python_version = "0.58.4"
 
 http_archive(
     name = "gapic_generator_python",
