feat: next release from main branch is 2.3.0 (#371)

Author: suztomo

Diff for: .github/release-please.yml

@@ -18,3 +18,7 @@ branches:
     bumpMinorPreMajor: true
     handleGHRelease: true
     branch: 2.1.x
+  - releaseType: java-backport
+    bumpMinorPreMajor: true
+    handleGHRelease: true
+    branch: 2.2.x

Diff for: .github/sync-repo-settings.yaml

@@ -47,6 +47,15 @@ branchProtectionRules:
     requiredApprovingReviewCount: 1
     requiresCodeOwnerReviews: true
     requiresStrictStatusChecks: true
+  - pattern: 2.2.x
+    isAdminEnforced: true
+    requiredStatusCheckContexts:
+      - units
+      - format
+      - cla/google
+    requiredApprovingReviewCount: 1
+    requiresCodeOwnerReviews: true
+    requiresStrictStatusChecks: true
 permissionRules:
   - team: Googlers
     permission: pull