Fix coverage output

Author: dorssel

.github/workflows/dotnet.yml

@@ -51,7 +51,7 @@ jobs:
       - name: Test
         run: |
           dotnet run --configuration Release --no-build --project Example
-          dotnet test --configuration Release --no-build -p:TestingPlatformCommandLineArguments="--report-trx --coverage"
+          dotnet test --configuration Release --no-build -p:TestingPlatformCommandLineArguments="--report-trx --coverage --coverage-output-format cobertura"
 
       - name: Package
         run: dotnet pack --configuration Release --no-build