Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/build.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Setup Java
         uses: actions/setup-java@v5

.github/workflows/deploy-apk.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Setup Java
         uses: actions/setup-java@v5