Remove remaining reference to <input type="datetime"> in SCSS comment

Erratum of #18778

[skip sauce]
[skip validator]

scss/_forms.scss

@@ -90,7 +90,7 @@
 // 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`.
+// Note that as of 8.3, iOS doesn't support `week`.
 
 @media screen and (-webkit-min-device-pixel-ratio: 0) {
   input[type="date"],