Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/build-test.yml

@@ -18,7 +18,7 @@ jobs:
     permissions:
       contents: read
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
       - uses: actions/setup-java@v3
         with:
           java-version: "8"

.github/workflows/deploy.yml

@@ -13,7 +13,7 @@ jobs:
     permissions:
       contents: read
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Cache Maven packages   # ←この行追加
         uses: actions/cache@v4
         with:

.github/workflows/released.yml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Cache Maven packages    # ←この行追加