Update actions plugin to v6

https://github.com/actions/checkout/blob/main/README.md#checkout-v6

JIRA: LIGHTY-378
Signed-off-by: tobias.pobocik <tobias.pobocik@pantheon.tech>

Author: Tobianas

.github/workflows/build.yml

@@ -19,7 +19,7 @@ jobs:
       SONAR_ORGANIZATION: ${{ secrets.SONAR_ORGANIZATION }}
       SONAR_PROJECT_KEY: ${{ secrets.SONAR_PROJECT_KEY}}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up JDK 21
         uses: actions/setup-java@v3
         with:

.github/workflows/publish-rcgnmi.yml

@@ -31,10 +31,10 @@ jobs:
     steps:
       - name: Clone Repository
         if: ${{ github.event.inputs.checkout-ref == 'default' }}
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: "Clone Repository, Ref: ${{ github.event.inputs.checkout-ref }}"
         if: ${{ github.event.inputs.checkout-ref != 'default' }}
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           ref: ${{ github.event.inputs.checkout-ref }}
       - name: Set up JDK 21

.github/workflows/publish-rnc.yml

@@ -31,10 +31,10 @@ jobs:
     steps:
       - name: Clone Repository
         if: ${{ github.event.inputs.checkout-ref == 'default' }}
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: "Clone Repository, Ref: ${{ github.event.inputs.checkout-ref }}"
         if: ${{ github.event.inputs.checkout-ref != 'default' }}
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           ref: ${{ github.event.inputs.checkout-ref }}
       - name: Set up JDK 21

.github/workflows/test-lighty-app.yml

@@ -21,7 +21,7 @@ jobs:
         shell: bash
     steps:
       - name: Clone Repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Set up JDK 21
         uses: actions/setup-java@v3
         with: