KT-6376 Smart completion should work after "in" and "!in"

#KT-6376 Fixed

idea/testData/completion/smart/inOperator/GenericMethod2.kt

@@ -0,0 +1,13 @@
+trait X<T> {
+    fun contains(t: T): Boolean
+}
+
+trait A {
+    fun<T> createX(t: T): X<T>
+
+    fun foo(s: String) {
+        if (s in <caret>)
+    }
+}
+
+// EXIST: { lookupString:"createX", itemText: "createX", tailText: "(t: T)", typeText:"X<T>" }