MdeModulePkg: Change OPTIONAL keyword usage style

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3760

Update all use of ', OPTIONAL' to ' OPTIONAL,' for function params.

Cc: Andrew Fish <afish@apple.com>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Michael Kubacki <michael.kubacki@microsoft.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>

MdeModulePkg/Library/CustomizedDisplayLib/CustomizedDisplayLib.c

@@ -404,7 +404,7 @@ UpdateStatusBar (
 VOID
 EFIAPI
 CreateDialog (
-  OUT EFI_INPUT_KEY  *Key,        OPTIONAL
+  OUT EFI_INPUT_KEY  *Key         OPTIONAL,
   ...
   )
 {
@@ -949,4 +949,3 @@ CustomizedDisplayLibDestructor (
 
   return EFI_SUCCESS;
 }
-