Revert "temporarily disable array.pos from test suite"
Revert "temporarily disable array.pos from test suite"

This reverts commit 26315d5972153f5552bdfbf514b28bc73742f622.

FStarLang/FStar,FStarLang/FStar,A-Manning/FStar,A-Manning/FStar,A-Manning/FStar,FStarLang/FStar