Bump langchain-google-genai from 4.2.0 to 4.2.1 (#5734)

Bumps [langchain-google-genai](https://github.com/langchain-ai/langchain-google) from 4.2.0 to 4.2.1.
- [Release notes](https://github.com/langchain-ai/langchain-google/releases)
- [Commits](langchain-ai/langchain-google@libs/genai/v4.2.0...libs/genai/v4.2.1)

---
updated-dependencies:
- dependency-name: langchain-google-genai
  dependency-version: 4.2.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements.txt

@@ -8,7 +8,7 @@ langchain==1.2.10
 langchain-anthropic==1.3.3
 langchain-classic==1.0.1
 langchain-community==0.4.1
-langchain-google-genai==4.2.0
+langchain-google-genai==4.2.1
 langchain-mistralai==1.1.1
 langchain-openai==1.1.9
 langgraph==1.0.8