chore: Update minimum version for pydantic.

PiperOrigin-RevId: 930768182

Author: wanlin31

pyproject.toml

@@ -28,7 +28,7 @@ dependencies = [
     "anyio>=4.8.0, <5.0.0",
     "google-auth[requests]>=2.48.1, <3.0.0",
     "httpx>=0.28.1, <1.0.0",
-    "pydantic>=2.9.0, <3.0.0",
+    "pydantic>=2.12.5, <3.0.0",
     "requests>=2.28.1, <3.0.0",
     "tenacity>=8.2.3, <9.2.0",
     "websockets>=13.0.0, <17.0",