Remove setup netcore action

Author: AlexNDRmac

.github/workflows/build-and-test.yml

@@ -56,12 +56,6 @@ jobs:
                   git fetch --prune --unshallow
                   git submodule -q update --init --recursive
 
-            - name: Setup DotNet SDK
-              if: (runner.os == 'macOS' || runner.os == 'Linux')
-              uses: actions/setup-dotnet@v1
-              with:
-                  dotnet-version: "3.1.x"
-
             - name: Setup nuget cache
               uses: actions/cache@v2
               id: nuget-cache