Update actions/checkout action to v6 (#317)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/main.yml

@@ -34,7 +34,7 @@ jobs:
       NUGET_PACKAGES: ${{ github.workspace }}/.github/nuget-packages
     steps:
     - name: Checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
     - name: NuGet cache
       uses: actions/cache@v4
       with:
@@ -53,13 +53,13 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
     - name: Check out the sources
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
     - name: REUSE license check
       uses: fsfe/reuse-action@v6
   encoding:
     runs-on: ubuntu-24.04
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Verify encoding
       shell: pwsh
       run: Scripts/Test-Encoding.ps1
@@ -71,7 +71,7 @@ jobs:
       NUGET_PACKAGES: ${{ github.workspace }}/.github/nuget-packages
     steps:
     - name: Check out the sources
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
     - name: Set up .NET SDK
       uses: actions/setup-dotnet@v5
     - name: NuGet cache

.github/workflows/release.yml

@@ -26,7 +26,7 @@ jobs:
       NUGET_PACKAGES: ${{ github.workspace }}/.github/nuget-packages
     steps:
     - name: Checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
     - id: version
       name: Read version from ref
       shell: pwsh