Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/compiler.yml

@@ -17,7 +17,7 @@ jobs:
       DOTNET_CLI_TELEMETRY_OPTOUT: 1
     steps:
       - name: Fetch the sources
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Set up .NET 6.0 SDK
         uses: actions/setup-dotnet@v1

.github/workflows/main.yml

@@ -24,7 +24,7 @@ jobs:
       DOTNET_CLI_TELEMETRY_OPTOUT: 1
     steps:
       - name: Fetch the sources
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Set up .NET 6.0 SDK
         uses: actions/setup-dotnet@v1

.github/workflows/sdk.yml

@@ -23,7 +23,7 @@ jobs:
         run: Write-Output "::set-output name=version::$($env:GITHUB_REF -replace '^refs/tags/v', '')"
 
       - name: Fetch the sources
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Set up .NET 6.0 SDK
         uses: actions/setup-dotnet@v1