Remove reference to old fixed WebKit bug in Less comment.

Per https://github.com/twbs/bootstrap/issues/1969#issuecomment-36971094

[skip sauce]
[skip validator]

less/forms.less

@@ -461,8 +461,7 @@ input[type="checkbox"] {
     }
 
     // Remove default margin on radios/checkboxes that were used for stacking, and
-    // then undo the floating of radios and checkboxes to match (which also avoids
-    // a bug in WebKit: https://github.com/twbs/bootstrap/issues/1969).
+    // then undo the floating of radios and checkboxes to match.
     .radio,
     .checkbox {
       display: inline-block;