082ed38 introduced it to fix the profile-per-install policy of FF 67. But since
FF 69 (or 68?), there is `MOZ_LEGACY_PROFILES`, which we use since 87e2618.
There is no reason for the `SNAP_NAME=firefox` workaround anymore.
Additionally, the combination of `SNAP_NAME=firefox` with
a large ~/.nix-profile/share in `XDG_DATA_DIRS` triggered
https://bugzilla.mozilla.org/show_bug.cgi?id=1569625 for me, so this really
fixes a bug in my configuration.
The only downside of this approach is that we lose support for running FF 67
(and possibly 68).
fa7004fd29