Drop deprecated pre-1.0 API. Remove remaining usages in tests.

compiler/testData/codegen/box/reflection/mapping/syntheticFields.kt

@@ -3,7 +3,7 @@
 
 // WITH_REFLECT
 
-import kotlin.reflect.jvm.kotlin
+import kotlin.reflect.jvm.kotlinProperty
 
 enum class A {
     // There's a synthetic field "$VALUES" here
@@ -11,7 +11,7 @@ enum class A {
 
 fun box(): String {
     for (field in A::class.java.getDeclaredFields()) {
-        val prop = field.kotlin
+        val prop = field.kotlinProperty
         if (prop != null) return "Fail, property found: $prop"
     }