jvm-minimal-for-test: apply module-wise -opt-in=kotlin.ExperimentalMultiplatform

Motivation: Consistency. All other stdlib modules use this module-wise
`-opt-in`

libraries/stdlib/jvm-minimal-for-test/build.gradle.kts

@@ -65,7 +65,8 @@ tasks.compileKotlin {
             "-Xallow-kotlin-package",
             "-Xmulti-platform",
             "-opt-in=kotlin.RequiresOptIn",
-            "-opt-in=kotlin.contracts.ExperimentalContracts"
+            "-opt-in=kotlin.contracts.ExperimentalContracts",
+            "-opt-in=kotlin.ExperimentalMultiplatform",
         )
         moduleName = "kotlin-stdlib"
     }

libraries/stdlib/jvm/runtime/kotlin/TypeAliases.kt

@@ -28,6 +28,5 @@ package kotlin
 @Suppress("NO_ACTUAL_CLASS_MEMBER_FOR_EXPECTED_CLASS")
 @SinceKotlin("1.3") public actual typealias ConcurrentModificationException = java.util.ConcurrentModificationException
 
-@OptIn(ExperimentalMultiplatform::class)
 @AllowDifferentMembersInActual // New 'reversed', 'thenComparing', etc. members are added compared to the expect declaration
 @SinceKotlin("1.1") public actual typealias Comparator<T> = java.util.Comparator<T>

libraries/stdlib/jvm/runtime/kotlin/text/TypeAliases.kt

@@ -7,7 +7,6 @@
 
 package kotlin.text
 
-@OptIn(ExperimentalMultiplatform::class)
 @AllowDifferentMembersInActual // New 'append' members are added compared to the expect declaration
 @SinceKotlin("1.1") public actual typealias Appendable = java.lang.Appendable