Stabilize new string and char case conversion API KT-45873

libraries/stdlib/js/src/kotlin/text/string.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2021 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.
  */
 
@@ -180,8 +180,8 @@ public actual inline fun String.toUpperCase(): String = asDynamic().toUpperCase(
  *
  * @sample samples.text.Strings.uppercase
  */
-@SinceKotlin("1.4")
-@ExperimentalStdlibApi
+@SinceKotlin("1.5")
+@WasExperimental(ExperimentalStdlibApi::class)
 @kotlin.internal.InlineOnly
 public actual inline fun String.uppercase(): String = asDynamic().toUpperCase()
 
@@ -199,8 +199,8 @@ public actual inline fun String.toLowerCase(): String = asDynamic().toLowerCase(
  *
  * @sample samples.text.Strings.lowercase
  */
-@SinceKotlin("1.4")
-@ExperimentalStdlibApi
+@SinceKotlin("1.5")
+@WasExperimental(ExperimentalStdlibApi::class)
 @kotlin.internal.InlineOnly
 public actual inline fun String.lowercase(): String = asDynamic().toLowerCase()