Maintainers: Update the VmgExitLib to CcExitLib

Maintainers: Update the VmgExitLib to CcExitLib

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4123

VmgExitLib is renamed as CcExitLib. The related section in
Maintainers.txt should be updated as well.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>