Fixed covr xml2 GitHub workflow issue

Author: Thomas-Rauter

.github/workflows/test-coverage.yaml

@@ -23,7 +23,7 @@ jobs:
 
       - uses: r-lib/actions/setup-r-dependencies@v2
         with:
-          extra-packages: any::covr
+          extra-packages: any::covr, any::xml2
           needs: coverage
 
       - name: Compute coverage (Cobertura XML)