chore(deps): update dependency langchain-google-vertexai to v3

Author: renovate-bot

samples/langchain_on_vertexai/requirements.txt

@@ -2,4 +2,4 @@ google-cloud-aiplatform[reasoningengine,langchain]==1.120.0
 google-cloud-resource-manager==1.14.2
 langchain-community==0.3.31
 langchain-google-cloud-sql-pg==0.14.1
-langchain-google-vertexai==2.1.2
+langchain-google-vertexai==3.0.0