docs(ReactionUserManager): fetch description (#5382)

The description currently says that fetching returns all users on the reaction.  This is incorrect, as there is an API limit of 100 users per fetch.  This PR changes the description to better match the actual behavior.

src/managers/ReactionUserManager.js

@@ -25,7 +25,7 @@ class ReactionUserManager extends BaseManager {
    */
 
   /**
-   * Fetches all the users that gave this reaction. Resolves with a collection of users, mapped by their IDs.
+   * Fetches the users that gave this reaction. Resolves with a collection of users, mapped by their IDs.
    * @param {Object} [options] Options for fetching the users
    * @param {number} [options.limit=100] The maximum amount of users to fetch, defaults to 100
    * @param {Snowflake} [options.before] Limit fetching users to those with an id lower than the supplied id