Update actions/checkout action to v6 (#10)

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

Author: renovate[bot]

.github/workflows/codeql.yml

@@ -39,7 +39,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
         submodules: recursive

.github/workflows/continuous.yml

@@ -11,7 +11,7 @@ jobs:
     name: build-pack
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Setup .NET SDK

.github/workflows/release.yml

@@ -20,7 +20,7 @@ jobs:
     env:
       VERSION: ${{ github.ref_name }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Setup .NET SDK

.github/workflows/update-material-symbols.yml

@@ -16,7 +16,7 @@ jobs:
     name: update
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Setup .NET SDK