Update 0311-task-locals.md (#1446)
Update 0311-task-locals.md (#1446)

* Update 0311-task-locals.md

Fixed a couple typos and clarified two ambiguous paragraphs.

* Apply suggestions from code review

Co-authored-by: Doug Gregor <20237f4b434bdcccb3b4c7b8643e049a656bb565@apple.com>
apple/swift-evolution,apple/swift-evolution,natecook1000/swift-evolution,abertelrud/swift-evolution,natecook1000/swift-evolution,abertelrud/swift-evolution