fix(ngAria): simplify aria-required attribute detection to support ng1.2.x
fix(ngAria): simplify aria-required attribute detection to support ng1.2.x

Remove the ngModel.$validators check to support angular 1.2.x. The check
serves no purpose but breaks aria on older angular versions.

KrekkieD/angular.js,KrekkieD/angular.js,KrekkieD/angular.js,KrekkieD/angular.js