feat: next release from main branch is 6.56.0 (#2929)

Author: lqiu96

.github/release-please.yml

@@ -30,3 +30,7 @@ branches:
     bumpMinorPreMajor: true
     handleGHRelease: true
     branch: 6.33.x
+  - releaseType: java-backport
+    bumpMinorPreMajor: true
+    handleGHRelease: true
+    branch: 6.55.x

.github/sync-repo-settings.yaml

@@ -122,6 +122,23 @@ branchProtectionRules:
       - checkstyle
       - compile (8)
       - compile (11)
+  - pattern: 6.55.x
+    isAdminEnforced: true
+    requiredApprovingReviewCount: 1
+    requiresCodeOwnerReviews: true
+    requiresStrictStatusChecks: false
+    requiredStatusCheckContexts:
+      - dependencies (17)
+      - lint
+      - javadoc
+      - units (8)
+      - units (11)
+      - 'Kokoro - Test: Integration'
+      - cla/google
+      - checkstyle
+      - compile (8)
+      - compile (11)
+      - OwlBot Post Processor
 permissionRules:
   - team: yoshi-admins
     permission: admin