Bump langchain from 0.3.25 to 0.3.26 (#5101)

Bumps [langchain](https://github.com/langchain-ai/langchain) from 0.3.25 to 0.3.26.
- [Release notes](https://github.com/langchain-ai/langchain/releases)
- [Commits](langchain-ai/langchain@langchain==0.3.25...langchain==0.3.26)

---
updated-dependencies:
- dependency-name: langchain
  dependency-version: 0.3.26
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

requirements.txt

@@ -2,7 +2,7 @@ amqp==5.3.1
 beautifulsoup4==4.13.4
 boto3==1.38.41
 imbalanced-learn==0.13.0
-langchain==0.3.25
+langchain==0.3.26
 langchain-anthropic==0.3.15
 langchain-community==0.3.25
 langchain-google-genai==2.1.5