Bump actions/checkout from 4 to 6

.github/workflows/Android.yml

@@ -30,7 +30,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up JDK 17
         uses: actions/setup-java@v4

.github/workflows/Linux_arm64.yml

@@ -30,7 +30,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Install dependency
         run: sudo apt-get update && sudo apt-get install -y libsdl2-dev

.github/workflows/Linux_arm64_AppImage.yml

@@ -24,7 +24,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Install dependency
         run: sudo apt-get update && sudo apt-get install -y libsdl2-dev

.github/workflows/Linux_x86_64.yml

@@ -30,7 +30,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Install dependency
         run: sudo apt-get update && sudo apt-get install -y libsdl2-dev

.github/workflows/Linux_x86_64_AppImage.yml

@@ -24,7 +24,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Install dependency
         run: sudo apt-get update && sudo apt-get install -y libsdl2-dev

.github/workflows/RaspberryPiOS_armhf.yml

@@ -25,7 +25,7 @@ jobs:
     runs-on: ubuntu-22.04
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Switch apt sources to ports.ubuntu.com for armhf
         run: |

.github/workflows/Windows_x86_x64_arm64.yml

@@ -30,7 +30,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       # SDL2 のセットアップをキャッシュし、必要ならスクリプトで実行
       - name: Cache SDL2

.github/workflows/macOS_Universal.yml

@@ -30,7 +30,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up Xcode 16.4
         uses: maxim-lobanov/setup-xcode@v1