docs: Add documentation for enums (#481)

* docs: Add documentation for enums

fix: Add context manager return types

chore: Update gapic-generator-python to v1.8.1
PiperOrigin-RevId: 503210727

Source-Link: googleapis/googleapis@a391fd1

Source-Link: googleapis/googleapis-gen@0080f83
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* 🦉 Updates from OwlBot post-processor

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

* work around docs issue

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

Author: gcf-owl-bot[bot]

packages/google-cloud-dlp/google/cloud/dlp_v2/services/dlp_service/client.py

@@ -4384,7 +4384,7 @@ def sample_finish_dlp_job():
             metadata=metadata,
         )
 
-    def __enter__(self):
+    def __enter__(self) -> "DlpServiceClient":
         return self
 
     def __exit__(self, type, value, traceback):