chore(deps): update actions/checkout action to v6 (#291)

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

.github/workflows/CI.yaml

@@ -15,7 +15,7 @@ jobs:
     name: Check format
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-dotnet@v5
         with:
           dotnet-version: ${{ env.NET_VERSION }}
@@ -32,7 +32,7 @@ jobs:
           - macos-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-dotnet@v5
         with:
           dotnet-version: ${{ env.NET_VERSION }}
@@ -42,7 +42,7 @@ jobs:
     needs: [test, check_format]
     runs-on: windows-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-dotnet@v5
         with:
           dotnet-version: ${{ env.NET_VERSION }}
@@ -70,7 +70,7 @@ jobs:
           - STUN
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-dotnet@v5
         with:
           dotnet-version: ${{ env.NET_VERSION }}