Coverage-reporting CI job: don't run lcov twice

cmake --target coverage already takes care of running lcov. We ended up
doing exactly the same work twice, just logging to different output
files. This should save about 90 seconds of CI job execution time.

Author: tautschnig

.github/workflows/pull-request-checks.yaml

@@ -699,15 +699,11 @@ jobs:
         run: cmake --build build -- -j2
       - name: Print ccache stats
         run: ccache -s
-      - name: Run CTest
+      - name: Run CTest and collect coverage statistics
         run: cmake --build build --target coverage -- -j2
-      - name: Collect coverage statistics
-        run: |
-          lcov --capture --directory build --output-file lcov.info
-          lcov --remove lcov.info '/usr/*' --output-file lcov.info
       - name: Upload coverage statistics to Codecov
         uses: codecov/codecov-action@v2
         with:
-          files: ./lcov.info
+          files: build/html/coverage.info
           fail_ci_if_error: true
           verbose: true