Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/Build_main_and_publish_to_nuget.yml

@@ -26,7 +26,7 @@ jobs:
     name: ubuntu-latest
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: 'Cache: .nuke/temp, ~/.nuget/packages'
         uses: actions/cache@v4
         with:

.github/workflows/Continuous_build.yml

@@ -23,7 +23,7 @@ jobs:
     name: ubuntu-latest
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: 'Cache: .nuke/temp, ~/.nuget/packages'
         uses: actions/cache@v4
         with:

.github/workflows/Manual_publish_to_Github_Nuget.yml

@@ -23,7 +23,7 @@ jobs:
     name: ubuntu-latest
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: 'Cache: .nuke/temp, ~/.nuget/packages'
         uses: actions/cache@v4
         with: