Update actions/checkout action to v7

Author: renovate[bot]

.github/workflows/gradle-build.yml

@@ -12,7 +12,7 @@ jobs:
         java: [ '21', '25' ]
 
     steps:
-    - uses: actions/checkout@v6
+    - uses: actions/checkout@v7
       with:
         fetch-depth: 1
         show-progress: false

.github/workflows/gradle-wrapper-validation.yml

@@ -9,7 +9,7 @@ jobs:
     name: "Validation"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
         with:
           fetch-depth: 1
           show-progress: false