Do not report NON_FINAL_MEMBER_IN_FINAL_CLASS on open members in enum classes

compiler/testData/diagnostics/tests/enum/openMemberInEnum.kt

@@ -0,0 +1,17 @@
+enum class EnumWithOpenMembers {
+    E1 {
+        override fun foo() = 1
+        override val bar: String = "a"
+    }
+
+    E2 {
+        <!OVERRIDING_FINAL_MEMBER!>override<!> fun f() = 3
+        <!OVERRIDING_FINAL_MEMBER!>override<!> val b = 4
+    }
+
+    open fun foo() = 1
+    open val bar: String = ""
+
+    fun f() = 2
+    val b = 3
+}