OvmfPkg/PlatformPei: Remove duplicate Xen memory map debug message

This duplicate message was intended to be removed from r15207
before it was committed. (It was pointed out by Wei Liu.)

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/OvmfPkg@15213 6f19259b-4bc3-4df7-8a09-765794883524