feat: next release from main branch is 2.31.0

Author: lqiu96

.github/release-please.yml

@@ -38,3 +38,9 @@ branches:
     extraFiles:
       - README.md
     branch: 2.22.x
+  - bumpMinorPreMajor: true
+    handleGHRelease: true
+    releaseType: java-backport
+    extraFiles:
+      - README.md
+    branch: 2.30.x

.github/sync-repo-settings.yaml

@@ -130,6 +130,23 @@ branchProtectionRules:
       - OwlBot Post Processor
       - 'Kokoro - Test: Java GraalVM Native Image'
       - 'Kokoro - Test: Java 17 GraalVM Native Image'
+  - pattern: 2.30.x
+    isAdminEnforced: true
+    requiredApprovingReviewCount: 1
+    requiresCodeOwnerReviews: true
+    requiresStrictStatusChecks: false
+    requiredStatusCheckContexts:
+      - dependencies (17)
+      - lint
+      - clirr
+      - units (8)
+      - units (11)
+      - 'Kokoro - Test: Integration'
+      - cla/google
+      - OwlBot Post Processor
+      - 'Kokoro - Test: Java GraalVM Native Image'
+      - 'Kokoro - Test: Java 17 GraalVM Native Image'
+      - javadoc
 permissionRules:
   - team: yoshi-admins
     permission: admin