Create from Usage: Add operator modifier to indexing get/set functions

#KT-10185 Fixed

idea/testData/quickfix/createFromUsage/createFunction/get/createGetFromUsage11.kt.after

@@ -1,6 +1,6 @@
 // "Create member function 'get'" "true"
 class Foo<T> {
-    fun get(s: String, w: T): T {
+    operator fun get(s: String, w: T): T {
         throw UnsupportedOperationException("not implemented") //To change body of created functions use File | Settings | File Templates.
     }
 }