Revert "[FE 1.0] Deprecate declaration of expect and actual in the same module"

This reverts commit b09561c3c3.

It was decided to postpone this warning till 1.9
This is needed to provide proper IDE support

^KT-40904 Open
^KT-55177 Open

libraries/stdlib/common/test/testUtils.kt

@@ -2,7 +2,6 @@
  * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
-@file:Suppress("EXPECT_AND_ACTUAL_IN_THE_SAME_MODULE")
 
 package test
 
@@ -34,4 +33,4 @@ public expect object BackReferenceHandling {
     val nonExistentGroup: HandlingOption
     val nonExistentNamedGroup: HandlingOption
     val groupZero: HandlingOption
-}
+}