Remove redundant @OptIn

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

@@ -108,7 +108,6 @@ public actual class StringBuilder actual constructor(content: String) : Appendab
     @SinceKotlin("1.4")
     @WasExperimental(ExperimentalStdlibApi::class)
     actual fun append(value: CharArray): StringBuilder {
-        @OptIn(ExperimentalStdlibApi::class)
         string += value.concatToString()
         return this
     }
@@ -238,7 +237,6 @@ public actual class StringBuilder actual constructor(content: String) : Appendab
     actual fun insert(index: Int, value: CharArray): StringBuilder {
         AbstractList.checkPositionIndex(index, length)
 
-        @OptIn(ExperimentalStdlibApi::class)
         string = string.substring(0, index) + value.concatToString() + string.substring(index)
         return this
     }
@@ -492,7 +490,6 @@ public actual class StringBuilder actual constructor(content: String) : Appendab
     @SinceKotlin("1.4")
     @WasExperimental(ExperimentalStdlibApi::class)
     public fun appendRange(value: CharArray, startIndex: Int, endIndex: Int): StringBuilder {
-        @OptIn(ExperimentalStdlibApi::class)
         string += value.concatToString(startIndex, endIndex)
         return this
     }
@@ -534,7 +531,6 @@ public actual class StringBuilder actual constructor(content: String) : Appendab
     public fun insertRange(index: Int, value: CharArray, startIndex: Int, endIndex: Int): StringBuilder {
         AbstractList.checkPositionIndex(index, this.length)
 
-        @OptIn(ExperimentalStdlibApi::class)
         string = string.substring(0, index) + value.concatToString(startIndex, endIndex) + string.substring(index)
         return this
     }

libraries/stdlib/js/src/kotlin/text/utf8Encoding.kt

@@ -6,7 +6,6 @@
 package kotlin.text
 
 /** Returns the negative [size] if [throwOnMalformed] is false, throws [CharacterCodingException] otherwise. */
-@OptIn(ExperimentalStdlibApi::class)
 private fun malformed(size: Int, index: Int, throwOnMalformed: Boolean): Int {
     if (throwOnMalformed) throw CharacterCodingException("Malformed sequence starting at ${index - 1}")
     return -size