Revert "Choose pipe number on initialize (#250)"

This reverts commit 4824b20f28.

include/discord_rpc.h

@@ -64,8 +64,7 @@ typedef struct DiscordEventHandlers {
 DISCORD_EXPORT void Discord_Initialize(const char* applicationId,
                                        DiscordEventHandlers* handlers,
                                        int autoRegister,
-                                       const char* optionalSteamId,
-                                       int optionalPipeNumber);
+                                       const char* optionalSteamId);
 DISCORD_EXPORT void Discord_Shutdown(void);
 
 /* checks for incoming messages, dispatches callbacks */