ShellPkg: fix RVCT warning due to CONST in typecast.

ShellPkg: fix RVCT warning due to CONST in typecast.

Building the latest shell on RVCT exposed this warning:

ShellPkg\Application\Shell\Shell.c(1090,69): error #191-D: type qualifier is meaningless on cast type

The CONST in the cast was deemed meaningless.  Removing the CONST fixed the warning.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Cohen Eugene <eugene@hp.com>
Reviewed-by: Qiu Shumin <shumin.qiu@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18954 6f19259b-4bc3-4df7-8a09-765794883524