ArmPlatformPkg: remove mention of ARMGCC and ARMLINUXGCC

ArmPlatformPkg: remove mention of ARMGCC and ARMLINUXGCC

Remove the ARMGCC and ARMLINUXGCC from comments in the respective
Makefiles of ArmPlatformPkg and ArmJunoPkg. Also drop the wildly
outdated Versatile Express instructions, since they refer to ARMGCC
as well.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18209 6f19259b-4bc3-4df7-8a09-765794883524