Do not suggest "Make overridden member open" for already open ones

So #KT-18148 Fixed

idea/testData/quickfix/override/overridingOpenMethodInFinalClass.kt

@@ -0,0 +1,11 @@
+// "Make A.foo open" "false"
+// ACTION: Convert to expression body
+// ERROR: 'foo' in 'A' is final and cannot be overridden
+// ERROR: This type is final, so it cannot be inherited from
+class A() {
+    open fun foo() {}
+}
+
+class B : A() {
+    override<caret> fun foo() { }
+}