Bump actions/checkout from 3 to 6 (#44)

Author: dependabot[bot]

.github/workflows/sdk-pr.yaml

@@ -26,7 +26,7 @@ jobs:
           distribution: "temurin"
           java-version: ${{ env.JAVA_VERSION }}
       - name: Checkout generator repo
-        uses: actions/checkout@v3
+        uses: actions/checkout@v6
         with:
           repository: "stackitcloud/stackit-sdk-generator"
           ref: "main"
@@ -60,7 +60,7 @@ jobs:
           distribution: "temurin"
           java-version: ${{ env.JAVA_VERSION }}
       - name: Checkout generator repo
-        uses: actions/checkout@v3
+        uses: actions/checkout@v6
         with:
           repository: "stackitcloud/stackit-sdk-generator"
           ref: "main"
@@ -101,7 +101,7 @@ jobs:
           distribution: "temurin"
           java-version: ${{ env.JAVA_VERSION }}
       - name: Checkout generator repo
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: "stackitcloud/stackit-sdk-generator"
           ref: "main"