Fixed completion for extension function after removing members for implicit receiver from scope.

idea/idea-completion/testData/basic/common/smartCast/MembersAfterSmartCast.kt

@@ -0,0 +1,21 @@
+interface A {
+    fun memberA()
+}
+
+interface B {
+    fun memberB()
+}
+
+interface C {
+    fun memberC()
+}
+
+fun C.test(a: Any) {
+    if (a is A && a is B) {
+        a.<caret>
+    }
+}
+
+// EXIST: memberA
+// EXIST: memberB
+// ABSENT: memberC