chore: allow releases on previous majors (#552)

* chore: allow releases on previous majors

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: parthea

packages/google-cloud-firestore/.github/release-please.yml

@@ -1,2 +1,11 @@
 releaseType: python
 handleGHRelease: 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
+  handleGHRelease: true
+  releaseType: python
+- branch: v0
+  handleGHRelease: true
+  releaseType: python

packages/google-cloud-firestore/owlbot.py

@@ -145,6 +145,8 @@ def update_fixup_scripts(library):
 
 python.py_samples(skip_readmes=True)
 
+python.configure_previous_major_version_branches()
+
 # ----------------------------------------------------------------------------
 # Customize noxfile.py
 # ----------------------------------------------------------------------------