Fix completion for private_to_this.

idea/testData/completion/basic/common/visibility/VisibilityClassMembersFromExternalForce.kt

@@ -0,0 +1,13 @@
+class Some() {
+    public val testPublic : Int = 12
+    protected val testProtected : Int = 12
+    private val testPrivate = 12
+    val testPackage = 12
+}
+
+fun test() {
+    Some().<caret>
+}
+
+// INVOCATION_COUNT: 2
+// EXIST: testPublic, testProtected, testPrivate, testPackage