Navigation to implementation: do not try to find expect enum inheritors

Before this commit, expect enum could find actual enum entries
as its implementation, now it cannot.
#KT-28206 Fixed

idea/testData/navigation/implementations/multiModule/expectEnumEntry/jvm/Some.kt

@@ -0,0 +1,6 @@
+package test
+
+actual enum class Some(val x: Int) {
+    FIRST(1),
+    SECOND(2)
+}