EmbeddedPkg: 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: Andrew Fish <afish@apple.com>

EmbeddedPkg/Library/PrePiExtractGuidedSectionLib/PrePiExtractGuidedSectionLib.c

@@ -167,7 +167,7 @@ EFIAPI
 ExtractGuidedSectionDecode (
   IN  CONST VOID    *InputSection,
   OUT       VOID    **OutputBuffer,
-  OUT       VOID    *ScratchBuffer,        OPTIONAL
+  OUT       VOID    *ScratchBuffer         OPTIONAL,
   OUT       UINT32  *AuthenticationStatus
   )
 {