Fix incorrect returning of completion entries when in string literal of property assignment expression

Fixes #11232

tests/cases/fourslash/completionListInObjectLiteralPropertyAssignment.ts

@@ -0,0 +1,15 @@
+/// <reference path='fourslash.ts' />
+
+////var foo;
+////interface I {
+////    metadata: string;
+////    wat: string;
+////}
+////var x: I = {
+////    metadata: "/*1*/
+////}
+
+goTo.marker('1');
+
+verify.not.completionListContains("metadata");
+verify.not.completionListContains("wat");