Fix the file path linked to grafana dashboards

From the #7 (comment 2803391486)

@nprabakaran I think the paths that we use when writing the result might be incorrect:

• ✅ test run for /explore works: link
• ❌ test run for /gitlab/-/blame/master/spec/models/project_spec.rb does not work: link

Notice the project_spec.rb/index.html part of the failed path, it tries to use project_spec.rb/ as a directory path but project_spec.rb/ is not a valid directory.