Correct 'allowed mentions' for reminder msgs when ctx msg is missing

Tasks/ReminderTasks.cs

@@ -76,6 +76,7 @@ public static async Task<bool> CheckRemindersAsync()
                         {
                             msg.WithContent($"<@{reminderObject.UserID}>, you asked to be reminded of something:");
                             msg.WithReply(null, false, false);
+                            msg.WithAllowedMentions(Mentions.All);
                             await channel.SendMessageAsync(msg);
                         }
                     }