Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/release.yml

@@ -25,7 +25,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up Go
         uses: actions/setup-go@v6

.github/workflows/test.yml

@@ -15,7 +15,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up Go
         uses: actions/setup-go@v6
@@ -43,7 +43,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up Go
         uses: actions/setup-go@v6