add comment, remove week type

less/forms.less

@@ -174,11 +174,12 @@ input[type="search"] {
 // text within the input to become vertically misaligned. As a workaround, we
 // set a pixel line-height that matches the given height of the input, but only
 // for Safari. See https://bugs.webkit.org/show_bug.cgi?id=139848
+//
+// Note that as of 8.3, iOS doesn't support `datetime` or `week`.
 
 @media screen and (-webkit-min-device-pixel-ratio: 0) {
   input[type="date"],
   input[type="time"],
-  input[type="week"],
   input[type="datetime-local"],
   input[type="month"] {
     &.form-control {