Converse the return value from 'int' to 'BOOLEAN' for function ‘ContainsSplit’ in Shell.c.

Signed-off-by: Shumin Qiu <shumin.qiu@intel.com>
Reviewed-by: Ni, Ruiyu <ruiyu.ni@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/ShellPkg@15006 6f19259b-4bc3-4df7-8a09-765794883524