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/Library/DxeHttpIoLib/DxeHttpIoLib.c

@@ -131,7 +131,7 @@ HttpIoCreateIo (
   IN EFI_HANDLE             Image,
   IN EFI_HANDLE             Controller,
   IN UINT8                  IpVersion,
-  IN HTTP_IO_CONFIG_DATA    *ConfigData, OPTIONAL
+  IN HTTP_IO_CONFIG_DATA    *ConfigData  OPTIONAL,
   IN HTTP_IO_CALLBACK       Callback,
   IN VOID                   *Context,
   OUT HTTP_IO               *HttpIo