[css-scroll-snap] Minor wording tweak to intro

Author: fantasai

css-scroll-snap/Overview.bs

@@ -189,12 +189,12 @@ Overview {#overview}
     for the scrollport to land on a <a>snap position</a>
     after scrolling operations.
 
-    <a>Snap positions</a> can be specified
+    <a>Snap positions</a> are specified
     as a particular alignment ('scroll-snap-align')
     of an element's <a>scroll snap area</a>
     (its border bounding box, as modified by 'scroll-snap-margin')
     within the <a>scroll container</a>’s <a>snapport</a>
-    (its scrollport, as reduced by its 'scroll-snap-padding').
+    (its scrollport, as reduced by 'scroll-snap-padding').
     This is conceptually equivalent to specifying the alignment of
     an <a>alignment subject</a> within an <a>alignment container</a>.
     A scroll position that satisfies the specified alignment