DEV: Remove Firefox browsers from Embeer tests in CI. (PR #14318)

This is making our CI take upwards of 45 mins.

Partial revert of 789613fe51733f108f97a926e22f409421e18fbc and 9b30fbdbbdf6c0af4811c606f5b1634e17fe833a

GitHub

The title of this pull request changed from “DEV: Remove Firefox browsers in CI.” to "DEV: Remove Firefox browsers from Embeer tests in CI.