Revert "Remove @PublishedApi from unwrap to comply with new compiler restriction (#3810)"

This reverts commit 2bd0f29.

Author: merfemor

kotlinx-coroutines-core/common/src/internal/StackTraceRecovery.common.kt

@@ -40,6 +40,7 @@ internal expect suspend inline fun recoverAndThrow(exception: Throwable): Nothin
  * The opposite of [recoverStackTrace].
  * It is guaranteed that `unwrap(recoverStackTrace(e)) === e`
  */
+@PublishedApi // published for the multiplatform implementation of kotlinx-coroutines-test
 internal expect fun <E: Throwable> unwrap(exception: E): E
 
 internal expect class StackTraceElement