correct bug tracker link in readme
correct bug tracker link in readme

was still pointing to *adwaita*…
synapsos/firefox-gnome,lbrfabio/firefox-gnome-flat,gnome-integration-team/firefox-gnome,gnome-integration-team/firefox-gnome,lbrfabio/firefox-gnome-flat,synapsos/firefox-gnome,lbrfabio/firefox-gnome-flat,synapsos/firefox-gnome,synapsos/firefox-gnome,gnome-integration-team/firefox-gnome,gnome-integration-team/firefox-gnome,lbrfabio/firefox-gnome-flat