[css-ui-4] Editorial tweaks to 'appearance'

Author: frivoal

css-ui-4/Overview.bs

@@ -282,8 +282,8 @@ Note: This specification intentionally refrains from making the appearance
 of all possible form controls and sub-controls available as values,
 as had previously been attempted by earlier proposals for this property
 and by several UA vendors in experimental implementations.
-Experience as shown that such a list would be extremely long and not practical to maintain,
-and UAs would need to add many non-standard values
+Experience as shown that such a list would be very long and not practical to maintain,
+and UAs would need to add non-standard values
 to account for the behavior of non-standard pseudo-elements
 sometimes used to implement form controls.
 Moreover, many values of such an enumeration only make sense