Move the Google GenAI Python integration to Public Preview (#5147)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: starfleeth

docs/develop/python/integrations/google-genai.mdx

@@ -33,7 +33,7 @@ History entry, and your credentials stay on the Worker.
 import { ReleaseNoteHeader } from '@site/src/components';
 
 <ReleaseNoteHeader
-  type="prerelease"
+  type="publicPreview"
 />
 
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