Fix eager copy/pasting of -c

Author: christophwille

.github/workflows/dotnet.yml

@@ -30,7 +30,7 @@ jobs:
       uses: actions/setup-dotnet@v1
       with:
         dotnet-version: 5.0.x
-    - run: dotnet restore ${{ env.Solution }} -c ${{ matrix.configuration }}
+    - run: dotnet restore ${{ env.Solution }}
     - name: Build
       run: dotnet build ${{ env.Solution }} --no-restore -c ${{ matrix.configuration }}
     - name: Test