Suppress UNCHECKED_CAST instead of CAST_NEVER_SUCCEEDS in several places

This is related to KT-6611 being fixed recently. Note that not all cases of
incorrect "cast never succeeds" were fixed

core/builtins/src/kotlin/ArrayIntrinsics.kt

@@ -22,5 +22,5 @@ import kotlin.internal.PureReifiable
  * Returns an empty array of the specified type [T].
  */
 public inline fun <reified @PureReifiable T> emptyArray(): Array<T> =
-        @Suppress("CAST_NEVER_SUCCEEDS")
-        arrayOfNulls<T>(0) as Array<T>
+        @Suppress("UNCHECKED_CAST")
+        (arrayOfNulls<T>(0) as Array<T>)

core/runtime.jvm/src/kotlin/jvm/internal/PrimitiveSpreadBuilders.kt

@@ -21,7 +21,7 @@ abstract class PrimitiveSpreadBuilder<T : Any>(private val size: Int) {
 
     protected var position: Int = 0
 
-    @Suppress("CAST_NEVER_SUCCEEDS")
+    @Suppress("UNCHECKED_CAST")
     private val spreads: Array<T?> = arrayOfNulls<Any>(size) as Array<T?>
 
     fun addSpread(spreadArgument: T) {