types(GuildChannelManager): correct fetch return type (v13)

src/managers/GuildChannelManager.js

@@ -324,7 +324,7 @@ class GuildChannelManager extends CachedManager {
    * Obtains one or more guild channels from Discord, or the channel cache if they're already available.
    * @param {Snowflake} [id] The channel's id
    * @param {BaseFetchOptions} [options] Additional options for this fetch
-   * @returns {Promise<?GuildChannel|Collection<Snowflake, GuildChannel>>}
+   * @returns {Promise<?(GuildChannel|ThreadChannel|Collection<Snowflake, GuildChannel>)>}
    * @example
    * // Fetch all channels from the guild (excluding threads)
    * message.guild.channels.fetch()

typings/index.d.ts

@@ -3232,7 +3232,7 @@ export class GuildChannelManager extends CachedManager<Snowflake, GuildBasedChan
     options?: ChannelWebhookCreateOptions,
   ): Promise<Webhook>;
   public edit(channel: GuildChannelResolvable, data: ChannelData, reason?: string): Promise<GuildChannel>;
-  public fetch(id: Snowflake, options?: BaseFetchOptions): Promise<NonThreadGuildBasedChannel | null>;
+  public fetch(id: Snowflake, options?: BaseFetchOptions): Promise<GuildBasedChannel | null>;
   public fetch(id?: undefined, options?: BaseFetchOptions): Promise<Collection<Snowflake, NonThreadGuildBasedChannel>>;
   public fetchWebhooks(channel: GuildChannelResolvable): Promise<Collection<Snowflake, Webhook>>;
   public setPosition(

typings/index.test-d.ts

@@ -910,7 +910,7 @@ declare const guildChannelManager: GuildChannelManager;
 
   expectType<Promise<Collection<Snowflake, AnyChannel>>>(guildChannelManager.fetch());
   expectType<Promise<Collection<Snowflake, AnyChannel>>>(guildChannelManager.fetch(undefined, {}));
-  expectType<Promise<AnyChannel | null>>(guildChannelManager.fetch('0'));
+  expectType<Promise<GuildBasedChannel | null>>(guildChannelManager.fetch('0'));
 }
 
 declare const roleManager: RoleManager;