KMP: Put "prohibit expect actual OptIn annotations" under the flag

^KT-61668 Fixed

Review: https://jetbrains.team/p/kt/reviews/12062/timeline

compiler/testData/diagnostics/tests/multiplatform/expectOptInAnnotation_oldLanguageVersion.kt

@@ -0,0 +1,19 @@
+// FIR_IDENTICAL
+// LANGUAGE: -MultiplatformRestrictions
+// WITH_STDLIB
+// MODULE: m1-common
+// FILE: common.kt
+@file:OptIn(ExperimentalMultiplatform::class)
+
+expect annotation class ActualOnly
+
+@RequiresOptIn
+expect annotation class Both
+
+// MODULE: m1-jvm()()(m1-common)
+// FILE: jvm.kt
+@RequiresOptIn
+actual annotation class ActualOnly
+
+@RequiresOptIn
+actual annotation class Both