Rename should not work on (unrelated) string literals

[amcasey]

Invoke Rename on one of the string literals below

function f() {
    return "function" + "function";
}

Expected: "You cannot rename this element" (as on, e.g., a keyword)
Actual: both instances are renamed

Tested in VS 2017 with both JS and TS files.

[amcasey]

FYI @RyanCavanaugh

[amcasey]

Same for character literals.