Update LABEL role definition

I updated the label role definition based on the latest feedback for Matt King and  Melanie Richards:
https://raw.githack.com/w3c/aria/issue-876-role-label/index.html#label

For the editors, I created a new pull request to get rid of the merge conflicts in the previous pull request.

Jon

Received on Thursday, 4 April 2019 21:51:08 UTC