chore: use gapic-generator-python 0.58.4 (#305)

* chore: use gapic-generator-python 0.58.4

fix: provide appropriate mock values for message body fields

committer: dovs
PiperOrigin-RevId: 419025932

Source-Link: googleapis/googleapis@73da669

Source-Link: googleapis/googleapis-gen@46df624
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* 🦉 Updates from OwlBot

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packages/google-cloud-dlp/google/cloud/dlp_v2/services/dlp_service/transports/base.py

@@ -100,7 +100,6 @@ def __init__(
             credentials, _ = google.auth.load_credentials_from_file(
                 credentials_file, **scopes_kwargs, quota_project_id=quota_project_id
             )
-
         elif credentials is None:
             credentials, _ = google.auth.default(
                 **scopes_kwargs, quota_project_id=quota_project_id