docs: add note about idempotence to role add/remove routes

#10586 djs

src/managers/GuildMemberRoleManager.js

@@ -100,6 +100,8 @@ class GuildMemberRoleManager extends DataManager {
 
   /**
    * Adds a role (or multiple roles) to the member.
+   *
+   * <info>Uses the idempotent PUT route for singular roles, otherwise PATCHes the underlying guild member</info>
    * @param {RoleResolvable|RoleResolvable[]|Collection<Snowflake, Role>} roleOrRoles The role or roles to add
    * @param {string} [reason] Reason for adding the role(s)
    * @returns {Promise<GuildMember>}
@@ -131,6 +133,8 @@ class GuildMemberRoleManager extends DataManager {
 
   /**
    * Removes a role (or multiple roles) from the member.
+   *
+   * <info>Uses the idempotent DELETE route for singular roles, otherwise PATCHes the underlying guild member</info>
    * @param {RoleResolvable|RoleResolvable[]|Collection<Snowflake, Role>} roleOrRoles The role or roles to remove
    * @param {string} [reason] Reason for removing the role(s)
    * @returns {Promise<GuildMember>}