Platforms/RaspberryPi: Set RPi4 Language supported to English

Set the supported RPi4 platform language to English (US),
and remove French.

This fixes https://github.com/pftf/RPi4/issues/35



Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Pete Batard <pete@akeo.ie>
Cc: Andrei Warkentin <awarkentin@vmware.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Signed-off-by: Samer El-Haj-Mahmoud <samer.el-haj-mahmoud@arm.com>
Reviewed-by: Pete Batard <pete@akeo.ie>
Reviewed-by: Andrei Warkentin <awarkentin@vmware.com>