Don't suggest making interface member final

(which was possible in leaking this inspection)
So #KT-14443 Fixed

idea/testData/inspectionsLocal/leakingThis/.inspection

@@ -0,0 +1 @@
+org.jetbrains.kotlin.idea.inspections.LeakingThisInspection

idea/testData/inspectionsLocal/leakingThis/noOpenForInterface.kt

@@ -0,0 +1,14 @@
+// PROBLEM: Calling non-final function foo in constructor
+
+interface My {
+    fun foo() {}
+}
+
+open class Your : My {
+
+    init {
+        // exactly one fix action should be here (make 'Your' final)
+        // making 'foo' final will provoke an error
+        <caret>foo()
+    }
+}

idea/testData/inspectionsLocal/leakingThis/noOpenForInterface.kt.after

@@ -0,0 +1,14 @@
+// PROBLEM: Calling non-final function foo in constructor
+
+interface My {
+    fun foo() {}
+}
+
+class Your : My {
+
+    init {
+        // exactly one fix action should be here (make 'Your' final)
+        // making 'foo' final will provoke an error
+        <caret>foo()
+    }
+}