chore(bazel): update Go generator version

Google APIs · copybara-github · commit 26faba69a6a4 · 2022-06-16T15:17:20.000-07:00
PiperOrigin-RevId: 455477948
diff --git a/WORKSPACE b/WORKSPACE
@@ -112,7 +112,7 @@ load("@bazel_gazelle//:deps.bzl", "gazelle_dependencies")
 
 gazelle_dependencies()
 
-_gapic_generator_go_version = "0.28.0"
+_gapic_generator_go_version = "0.31.0"
 
 http_archive(
     name = "com_googleapis_gapic_generator_go",
