UnnecessaryVariableInspection: don't report for overriding property

#KT-39263 Fixed

idea/testData/inspectionsLocal/unnecessaryVariable/override.kt

@@ -0,0 +1,17 @@
+// PROBLEM: none
+abstract class Foo {
+    abstract val bar: Int
+    abstract fun baz()
+}
+
+fun println(i: Int) {}
+
+fun test() {
+    val i = 1
+    object : Foo() {
+        override val <caret>bar = i
+        override fun baz() {
+            println(bar)
+        }
+    }
+}