Add 'global' region to Google provider options

Author: aelmiger

pydantic_ai_slim/pydantic_ai/providers/google.py

@@ -165,6 +165,7 @@ def __init__(
     'europe-west6',
     'europe-west8',
     'europe-west9',
+    'global',
     'me-central1',
     'me-central2',
     'me-west1',