NetworkPkg: 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: Maciej Rabeda <maciej.rabeda@linux.intel.com>

NetworkPkg/TcpDxe/TcpDriver.c

@@ -411,7 +411,7 @@ TcpDestroyService (
   IN EFI_HANDLE  Controller,
   IN EFI_HANDLE  ImageHandle,
   IN UINTN       NumberOfChildren,
-  IN EFI_HANDLE  *ChildHandleBuffer, OPTIONAL
+  IN EFI_HANDLE  *ChildHandleBuffer  OPTIONAL,
   IN UINT8       IpVersion
   )
 {