fix: remove support for overriding caches that break functionality (#6282)

Co-authored-by: Noel <buechler.noel@outlook.com>

src/managers/GuildChannelManager.js

@@ -9,6 +9,8 @@ const PermissionOverwrites = require('../structures/PermissionOverwrites');
 const ThreadChannel = require('../structures/ThreadChannel');
 const { ChannelTypes, ThreadChannelTypes } = require('../util/Constants');
 
+let cacheWarningEmitted = false;
+
 /**
  * Manages API methods for GuildChannels and stores their cache.
  * @extends {CachedManager}
@@ -16,6 +18,13 @@ const { ChannelTypes, ThreadChannelTypes } = require('../util/Constants');
 class GuildChannelManager extends CachedManager {
   constructor(guild, iterable) {
     super(guild.client, GuildChannel, iterable);
+    if (!cacheWarningEmitted && this._cache.constructor.name !== 'Collection') {
+      cacheWarningEmitted = true;
+      process.emitWarning(
+        `Overriding the cache handling for ${this.constructor.name} is unsupported and breaks functionality.`,
+        'UnuspportedCacheOverwriteWarning',
+      );
+    }
 
     /**
      * The guild this Manager belongs to