Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
 
       - name: Build
         uses: eskatos/gradle-command-action@v2.10.0

.github/workflows/release.yml

@@ -15,7 +15,7 @@ jobs:
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
 
       - name: Build
         uses: eskatos/gradle-command-action@v2.10.0