stack/erp5: don't produce HTML report for each test

The coverage of an individual test is after all not useful, only the
coverage of all tests combined is significant.

stack/erp5/buildout.cfg

@@ -417,11 +417,6 @@ initialization =
     if coverage_process:
       coverage_process.stop()
       coverage_process.save()
-      # Make html report for this test
-      os.chdir(buildout_directory)
-      coverage_process.html_report(
-        directory=os.path.join(assets_directory, 'coverage_report'),
-      )
       # upload the coverage so that they can be combined from another machine
       upload_url = test_runner_configuration['coverage'].get('upload-url')
       if upload_url: