fix(GuildTemplate): 'guild' getter (#5040)

Author: izexi

src/structures/GuildTemplate.js

@@ -198,8 +198,9 @@ class GuildTemplate extends Base {
    * @readonly
    */
   get guild() {
-    return this.client.guilds.get(this.guildID) || null;
+    return this.client.guilds.cache.get(this.guildID) || null;
   }
+
   /**
    * The URL of this template
    * @type {string}