Comparison typeof with undefined (not "undefined" string) in commandParser #16660

Recent PR #12336 Use parser to parse tsconfig json instead of using Json.parse contained an apparent bug:

if (typeof keyText !== undefined && typeof value !== undefined) {

typeof operator can never produce undefined, it's guaranteed to return a string for any value.

Andy (Andrewkraft) (@Andy-MS) have noticed it, but it's got lost in the large review.

Here is the link to that place on the master branch for convenience. It still compares typeof to undefined: commandLineParser.ts#L1056