[K/N] Adjust moved special backend checks tests

^KT-61564

compiler/testData/diagnostics/nativeTests/specialBackendChecks/objCInterop/t26.kt

@@ -1,8 +1,12 @@
+// FIR_IDENTICAL
+// WITH_PLATFORM_LIBS
 import kotlinx.cinterop.*
 import platform.darwin.*
 import platform.Foundation.*
 
+@OptIn(kotlinx.cinterop.ExperimentalForeignApi::class)
 class Zzz : NSAssertionHandler() {
+    @OptIn(kotlinx.cinterop.BetaInteropApi::class)
     @ObjCAction
     fun String.foo() = println(this)
 }