use lodash for unique function instead of rolling our own

src/ArrayUtils.js

@@ -1,30 +0,0 @@
-/*
-Copyright 2018 New Vector
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-/**
- * creates a new array with only the unique values of the given array
- * @param {array} arr the array to deduplicate
- * @return {array} the deduplicated array
- */
-export function unique(arr) {
-    const cpy = [];
-    arr.forEach((el) => {
-        if (!cpy.includes(el)) {
-            cpy.push(el);
-        }
-    });
-    return cpy;
-}

src/utils/DMRoomMap.js

@@ -15,7 +15,7 @@ limitations under the License.
 */
 
 import MatrixClientPeg from '../MatrixClientPeg';
-import {unique} from '../ArrayUtils';
+import _uniq from 'lodash/uniq';
 
 /**
  * Class that takes a Matrix Client and flips the m.direct map
@@ -109,7 +109,7 @@ export default class DMRoomMap {
                     userToRooms[userId] = [roomId];
                 } else {
                     roomIds.push(roomId);
-                    userToRooms[userId] = unique(roomIds);
+                    userToRooms[userId] = _uniq(roomIds);
                 }
             });
             return true;