chore: update release-please.yml branch name for Python client library cherrypick release

PiperOrigin-RevId: 660903697

Author: yinghsienwu

.github/release-please.yml

@@ -4,7 +4,7 @@ manifest: true
 # NOTE: this section is generated by synthtool.languages.python
 # See https://github.com/googleapis/synthtool/blob/master/synthtool/languages/python.py
 branches:
-- branch: v1.54
+- branch: v1.61
   handleGHRelease: true
   releaseType: python
   manifest: true