fix: link to 'Front page' from run report — radicle-ci-broker

Individual report pages are generated under report_dir from the cib config, which is the directory which contains the summary index.html page so there’s no need to link to the parent.

         doc.push_to_body(
             Element::new(Tag::P).with_child(
                 Element::new(Tag::A)
                     .with_attribute("href", "../index.html")
                     .with_attribute("href", "./index.html")
                     .with_text("Front page"),
             ),
         );