update checkout action

.github/workflows/dotnetcore.yml

@@ -4,16 +4,12 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v1
-    - name: Setup .NET Core
-      uses: actions/setup-dotnet@v1
-      with:
-        dotnet-version: 2.2.108
-    - name: Build with dotnet
-      run: dotnet build --configuration Release
-    - name: Test
-      run: dotnet test src/PostalCodes.UnitTests/PostalCodes.UnitTests.csproj
-    - name: Publish
-      run: |
-        dotnet pack . -p:PackageVersion=3.1.0.6 -o .
-        dotnet nuget push src/PostalCodes/PostalCodes.3.1.0.6.nupkg -k ${{ secrets.NUGET_API_KEY }} -s https://api.nuget.org/v3/index.json
+      - uses: actions/checkout@v4
+      - name: Setup .NET Core
+        uses: actions/setup-dotnet@v1
+        with:
+          dotnet-version: 2.2.108
+      - name: Build with dotnet
+        run: dotnet build --configuration Release
+      - name: Test
+        run: dotnet test src/PostalCodes.UnitTests/PostalCodes.UnitTests.csproj