Unpin selenium-chrome once SCORM problems are sorted

[stronk7]

With #22, we pinned selenium-chrome to use Chome 79 because Chrome 80 was adding too much noise to builds.

Once https://tracker.moodle.org/browse/MDL-67989 is solved, we can revert that commit in order to get again Chome 80 onboard.

Just that, ciao :-)