chore: Update gapic-generator-python to v1.8.4 (#192)

* chore: Update gapic-generator-python to v1.8.4

PiperOrigin-RevId: 507808936

Source-Link: googleapis/googleapis@64cf849

Source-Link: googleapis/googleapis-gen@53c48ca
Copy-Tag: eyJwIjoiLmdpdGh1Yi8uT3dsQm90LnlhbWwiLCJoIjoiNTNjNDhjYWMxNTNkM2IzN2YzZDJjMmRlYzQ4MzBjZmQ5MWVjNDE1MyJ9

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

packages/google-cloud-eventarc/setup.py

@@ -56,9 +56,7 @@
     if package.startswith("google")
 ]
 
-namespaces = ["google"]
-if "google.cloud" in packages:
-    namespaces.append("google.cloud")
+namespaces = ["google", "google.cloud"]
 
 setuptools.setup(
     name=name,