Add Google Gemini 3.1 verify models (#2276)

Co-authored-by: Juan Michelini <juan@juan.com.uy>

Author: mayeco

openhands-sdk/openhands/sdk/llm/utils/verified_models.py

@@ -48,6 +48,7 @@
 
 VERIFIED_GEMINI_MODELS = [
     "gemini-3-pro-preview",
+    "gemini-3.1-pro-preview",
 ]
 
 VERIFIED_DEEPSEEK_MODELS = [
@@ -71,6 +72,7 @@
     "gpt-5.2-codex",
     "minimax-m2.5",
     "gemini-3-pro-preview",
+    "gemini-3.1-pro-preview",
     "deepseek-chat",
     "kimi-k2-thinking",
     "kimi-k2.5",