[css-text] Fix stray text from when word-spacing took percentages

Part of w3c#2165

Author: frivoal

css-text-3/Overview.bs

@@ -1913,7 +1913,7 @@ Word Spacing: the 'word-spacing' property</h3>
   Applies to: <a>inline boxes</a>
   Inherited: yes
   Percentages: N/A
-  Computed value: the keyword ''word-spacing/normal'' or a computed <<length-percentage>> value
+  Computed value: the keyword ''word-spacing/normal'' or an absolute length
   Animation type: by computed value type
   Canonical order: n/a
   </pre>