chore: allow releases from previous major branches (#429)

Author: busunkim96

packages/google-cloud-bigquery-storage/.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-bigquery-storage/owlbot.py

@@ -142,8 +142,7 @@
     templated_files, excludes=[".coveragerc"]
 )  # microgenerator has a good .coveragerc file
 
-# Work around bug in templates https://github.com/googleapis/synthtool/pull/1335
-s.replace(".github/workflows/unittest.yml", "--fail-under=100", "--fail-under=98")
+python.configure_previous_major_version_branches()
 
 # ----------------------------------------------------------------------------
 # Samples templates