UI: Use fa-gitlab in the "about" window
As a follow-up of nodes/typescript/duniter#1267 (closed), fontawesome should be upgrade to v4.6 in order to use fa-gitlab rather than fa-github in the "about" window.
As a follow-up of nodes/typescript/duniter#1267 (closed), fontawesome should be upgrade to v4.6 in order to use fa-gitlab rather than fa-github in the "about" window.