Add Google GitHub Action creds file to gitignore. (#11296)

Should resolve the issue here:
https://github.com/langchain-ai/langchain/actions/runs/6342767671/job/17229204508#step:7:36

After this merges, we can revert
https://github.com/langchain-ai/langchain/pull/11192

.gitignore

@@ -30,6 +30,12 @@ share/python-wheels/
 *.egg
 MANIFEST
 
+# Google GitHub Actions credentials files created by:
+# https://github.com/google-github-actions/auth
+#
+# That action recommends adding this gitignore to prevent accidentally committing keys.
+gha-creds-*.json
+
 # PyInstaller
 #  Usually these files are written by a python script from a template
 #  before PyInstaller builds the exe, so as to inject date/other infos into it.