[css-snappoints] Consistently use double quote for attribute values

Author: ChumpChief

css-snappoints/Overview.bs

@@ -1,4 +1,4 @@
-<pre class='metadata'>
+<pre class="metadata">
 Title: CSS Scroll Snap Points Module Level 1
 Group: csswg
 Shortname: css-snappoints
@@ -212,7 +212,7 @@ Scroll Snap Types: the 'scroll-snap-type' property {#scroll-snap-type}
 
     Issue: Currently considering renaming the values
 
-    <pre class='propdef'>
+    <pre class="propdef">
     Name: scroll-snap-type
     Value: none | mandatory | proximity
     Initial: none