Update actions/checkout action to v6 (#183)

Author: renovate[bot]

.github/workflows/gradle-checks.yml

@@ -15,7 +15,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: set up JDK 17
         uses: actions/setup-java@v5
@@ -42,7 +42,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: set up JDK 17
         uses: actions/setup-java@v5
@@ -75,7 +75,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: set up JDK 17
         uses: actions/setup-java@v5

.github/workflows/ktlint.yml

@@ -18,7 +18,7 @@ jobs:
 
       - name: "checkout"
         if: env.changed_kotlin_files != ''
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Install ktlint
         if: env.changed_kotlin_files != ''