Remove unused utility

src/utils/css.ts

@@ -1,30 +0,0 @@
-/*
-Copyright 2020 The Matrix.org Foundation C.I.C.
-
-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.
-*/
-
-export function addClass(classes: string, clazz: string): string {
-    if (!classes.includes(clazz)) return `${classes} ${clazz}`;
-    return classes;
-}
-
-export function removeClass(classes: string, clazz: string): string {
-    const idx = classes.indexOf(clazz);
-    if (idx >= 0) {
-        const beforeStr = classes.substring(0, idx);
-        const afterStr =  classes.substring(idx + clazz.length);
-        return `${beforeStr} ${afterStr}`.trim();
-    }
-    return classes;
-}