Upgrade GHA reusable workflows from main to v6

Author: artembilan

.github/workflows/backport-issue.yml

@@ -7,6 +7,6 @@ on:
 
 jobs:
   backport-issue:
-    uses: spring-io/spring-github-workflows/.github/workflows/spring-backport-issue.yml@main
+    uses: spring-io/spring-github-workflows/.github/workflows/spring-backport-issue.yml@v6
     secrets:
       GH_ACTIONS_REPO_TOKEN: ${{ secrets.GH_ACTIONS_REPO_TOKEN }}

.github/workflows/pr-build.yml

@@ -8,4 +8,4 @@ on:
 
 jobs:
   build-pull-request:
-    uses: spring-io/spring-github-workflows/.github/workflows/spring-gradle-pull-request-build.yml@main
+    uses: spring-io/spring-github-workflows/.github/workflows/spring-gradle-pull-request-build.yml@v6

.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@v6
     secrets:
       GH_ACTIONS_REPO_TOKEN: ${{ secrets.GH_ACTIONS_REPO_TOKEN }}
       DEVELOCITY_ACCESS_KEY: ${{ secrets.DEVELOCITY_ACCESS_KEY }}