IceCatMobile: remove note about non-free addons
IceCatMobile: remove note about non-free addons

IceCatMobile -> Tools -> Add-ons -> Browse all Firefox Add-ons opens
https://directory.fsf.org/wiki/IceCat, not addons.mozilla.org.

Closes fdroid/fdroiddata#1084.

f-droid/fdroiddata,f-droid/fdroiddata,f-droid/fdroid-data