remove unneeded CollectionUtil and Either.java (#1201)

app/src/main/java/com/keylesspalace/tusky/util/CollectionUtil.java

@@ -1,38 +0,0 @@
-/* Copyright 2017 Andrew Dawson
- *
- * This file is a part of Tusky.
- *
- * This program is free software; you can redistribute it and/or modify it under the terms of the
- * GNU General Public License as published by the Free Software Foundation; either version 3 of the
- * License, or (at your option) any later version.
- *
- * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
- * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
- * Public License for more details.
- *
- * You should have received a copy of the GNU General Public License along with Tusky; if not,
- * see <http://www.gnu.org/licenses>. */
-package com.keylesspalace.tusky.util;
-
-import androidx.arch.core.util.Function;
-
-import java.util.ArrayList;
-import java.util.List;
-
-/**
- * Created by charlag on 05/11/17.
- */
-
-public final class CollectionUtil {
-    private CollectionUtil() {
-        throw new AssertionError();
-    }
-
-    public static <E, R> List<R> map(List<E> list, Function<E, R> mapper) {
-        final List<R> newList = new ArrayList<>(list.size());
-        for (E el : list) {
-            newList.add(mapper.apply(el));
-        }
-        return newList;
-    }
-}