Remove redundant border radius on pagination

Created by: MartijnCuppens

Pagination used to have box shadow back in the days which required this property, but nowadays it's redundant. (see https://github.com/twbs/bootstrap/blame/0cd186183c5e18f0517d6037d53f29c56adbac72/less/pagination.less#L17)

requested review from @ghost

added css no-backport-to-v4 v5 labels

closed