Upgrade WFs from main to v4

The `v3` has to be updated by Dependabot automatically

**Auto-cherry-pick to `3.2.x` & `3.1.x`**

.github/workflows/announce-milestone-planning.yml

@@ -6,6 +6,6 @@ on:
 
 jobs:
   announce-milestone-planning:
-    uses: spring-io/spring-github-workflows/.github/workflows/spring-announce-milestone-planning.yml@main
+    uses: spring-io/spring-github-workflows/.github/workflows/spring-announce-milestone-planning.yml@v4
     secrets:
       SPRING_RELEASE_CHAT_WEBHOOK_URL: ${{ secrets.SPRING_RELEASE_GCHAT_WEBHOOK_URL }}

.github/workflows/ci-snapshot.yml

@@ -17,7 +17,7 @@ concurrency:
 
 jobs:
   build-snapshot:
-    uses: spring-io/spring-github-workflows/.github/workflows/spring-artifactory-gradle-snapshot.yml@main
+    uses: spring-io/spring-github-workflows/.github/workflows/spring-artifactory-gradle-snapshot.yml@v4
     with:
       gradleTasks: ${{ github.event_name == 'schedule' && '--rerun-tasks' || '' }}
     secrets:

.github/workflows/merge-dependabot-pr.yml

@@ -12,7 +12,7 @@ jobs:
   merge-dependabot-pr:
     permissions: write-all
 
-    uses: spring-io/spring-github-workflows/.github/workflows/spring-merge-dependabot-pr.yml@main
+    uses: spring-io/spring-github-workflows/.github/workflows/spring-merge-dependabot-pr.yml@v4
     with:
       mergeArguments: --auto --squash
       autoMergeSnapshots: true

.github/workflows/release.yml

@@ -12,7 +12,7 @@ jobs:
       contents: write
       issues: write
 
-    uses: spring-io/spring-github-workflows/.github/workflows/spring-artifactory-gradle-release.yml@main
+    uses: spring-io/spring-github-workflows/.github/workflows/spring-artifactory-gradle-release.yml@v4
     secrets:
       GH_ACTIONS_REPO_TOKEN: ${{ secrets.GH_ACTIONS_REPO_TOKEN }}
       DEVELOCITY_ACCESS_KEY: ${{ secrets.DEVELOCITY_ACCESS_KEY }}