Fix doc wording around covariance/invariance

libraries/stdlib/src/kotlin/collections/AbstractCollection.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 package kotlin.collections
@@ -9,7 +9,7 @@ import kotlin.js.JsName
 /**
  * Provides a skeletal implementation of the read-only [Collection] interface.
  *
- * @param E the type of elements contained in the collection. The collection is covariant on its element type.
+ * @param E the type of elements contained in the collection. The collection is covariant in its element type.
  */
 @SinceKotlin("1.1")
 public abstract class AbstractCollection<out E> protected constructor() : Collection<E> {

libraries/stdlib/src/kotlin/collections/AbstractList.kt

@@ -1,7 +1,8 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
+
 /*
  * Based on GWT AbstractList
  * Copyright 2007 Google Inc.
@@ -14,7 +15,7 @@ package kotlin.collections
  *
  * This class is intended to help implementing read-only lists so it doesn't support concurrent modification tracking.
  *
- * @param E the type of elements contained in the list. The list is covariant on its element type.
+ * @param E the type of elements contained in the list. The list is covariant in its element type.
  */
 @SinceKotlin("1.1")
 public abstract class AbstractList<out E> protected constructor() : AbstractCollection<E>(), List<E> {

libraries/stdlib/src/kotlin/collections/AbstractMap.kt

@@ -1,7 +1,8 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
+
 /*
  * Based on GWT AbstractMap
  * Copyright 2007 Google Inc.
@@ -14,8 +15,8 @@ package kotlin.collections
  *
  * The implementor is required to implement [entries] property, which should return read-only set of map entries.
  *
- * @param K the type of map keys. The map is invariant on its key type.
- * @param V the type of map values. The map is covariant on its value type.
+ * @param K the type of map keys. The map is invariant in its key type.
+ * @param V the type of map values. The map is covariant in its value type.
  */
 @SinceKotlin("1.1")
 public abstract class AbstractMap<K, out V> protected constructor() : Map<K, V> {

libraries/stdlib/src/kotlin/collections/AbstractSet.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 package kotlin.collections
@@ -9,7 +9,7 @@ package kotlin.collections
  *
  * This class is intended to help implementing read-only sets so it doesn't support concurrent modification tracking.
  *
- * @param E the type of elements contained in the set. The set is covariant on its element type.
+ * @param E the type of elements contained in the set. The set is covariant in its element type.
  */
 @SinceKotlin("1.1")
 public abstract class AbstractSet<out E> protected constructor() : AbstractCollection<E>(), Set<E> {