Doc: sync Android requirements with the Qt docs

It would be better to have this information only in one
place, but as we have it in several places, it should at
least be the same information everywhere.

Change-Id: Ib599a25156780f8f897ad87d0dce9c968a32098b
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>