Fix doc wording around covariance/invariance

libraries/stdlib/common/src/kotlin/collections/AbstractMutableCollection.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.
  */
 
@@ -8,7 +8,7 @@ package kotlin.collections
 /**
  * Provides a skeletal implementation of the [MutableCollection] interface.
  *
- * @param E the type of elements contained in the collection. The collection is invariant on its element type.
+ * @param E the type of elements contained in the collection. The collection is invariant in its element type.
  */
 @SinceKotlin("1.3")
 public expect abstract class AbstractMutableCollection<E> : MutableCollection<E> {

libraries/stdlib/common/src/kotlin/collections/AbstractMutableList.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.
  */
 
@@ -8,7 +8,7 @@ package kotlin.collections
 /**
  * Provides a skeletal implementation of the [MutableList] interface.
  *
- * @param E the type of elements contained in the list. The list is invariant on its element type.
+ * @param E the type of elements contained in the list. The list is invariant in its element type.
  */
 public expect abstract class AbstractMutableList<E> : MutableList<E> {
     protected constructor()

libraries/stdlib/common/src/kotlin/collections/AbstractMutableMap.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.
  */
 
@@ -10,8 +10,8 @@ package kotlin.collections
  *
  * The implementor is required to implement [entries] property, which should return mutable set of map entries, and [put] function.
  *
- * @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 invariant 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 invariant in its value type.
  */
 @SinceKotlin("1.3")
 public expect abstract class AbstractMutableMap<K, V> : MutableMap<K, V> {

libraries/stdlib/common/src/kotlin/collections/AbstractMutableSet.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.
  */
 
@@ -8,7 +8,7 @@ package kotlin.collections
 /**
  * Provides a skeletal implementation of the [MutableSet] interface.
  *
- * @param E the type of elements contained in the set. The set is invariant on its element type.
+ * @param E the type of elements contained in the set. The set is invariant in its element type.
  */
 @SinceKotlin("1.3")
 public expect abstract class AbstractMutableSet<E> : MutableSet<E> {