adjust discordjs client dummy type to fully allow the typings from v13

TLDR; if we define missing keys as undefined in the type TS forces us to still set the key, which is not the behaviour we want, as the client just doesn't have the key set at all

Author: maybeanerd

src/main.ts

@@ -53,10 +53,7 @@ type DiscordJSClientFallback = {
   guilds: {
     cache: Collection<
       string,
-      (
-        | { shardID: number; shardId: undefined }
-        | { shardId: number; shardID: undefined }
-      ) & { [k: string]: any }
+      ({ shardID: number } | { shardId: number }) & { [k: string]: any }
     >;
   };
   ws: {