See if can skip setting up dotnet (#157)

* Update pull-request.yaml

* Update pull-request.yaml

.github/workflows/pull-request.yaml

@@ -22,29 +22,8 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Install .NET Core SDK 2.1
-        uses: actions/setup-dotnet@v1
-        with:
-          dotnet-version: '2.1.x'
-
-      - name: Install .NET Core SDK 3.1
-        uses: actions/setup-dotnet@v1
-        with:
-          dotnet-version: '3.1.x'
-
-      - name: Install .NET SDK 5.0
-        uses: actions/setup-dotnet@v1
-        with:
-          dotnet-version: '5.0.x'
-
       - name: Get .NET information
         run: dotnet --info
-        
-      - name: Clean
-        run: dotnet clean -v m
-        
-      - name: Clear cache
-        run: dotnet nuget locals all --clear
 
       - name: Build
         run: dotnet build -c ${{ matrix.config }}