Update actions/checkout action to v7

Author: renovate[bot]

.github/workflows/main.yml

@@ -38,7 +38,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: Verify encoding
         shell: pwsh

.github/workflows/nuget.yml

@@ -22,7 +22,7 @@ jobs:
       NUGET_PACKAGES: ${{ github.workspace }}/.github/nuget-packages
     steps:
       - name: Checkout
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: Read version from ref
         id: version