[css-text-decor-3] Fix typos. w3c#2286

Author: fantasai

css-text-decor-3/Overview.bs

@@ -263,7 +263,7 @@ Text Decoration Lines: the 'text-decoration-line' property</h3>
   </dl>
 
     Note: In <a>vertical writing modes</a>,
-    'text-decoration-position' can cause the underline and overline to switch sides.
+    'text-underline-position' can cause the underline and overline to switch sides.
     This allows the position of underlines to key off of language-specific preferences
     automatically.
 
@@ -345,7 +345,7 @@ Text Decoration Shorthand: the 'text-decoration' property</h3>
 <!-- -->}</code></pre>
   </div>
 
-  Note: The shorthand purposefully omits the 'text-decoration-position' property,
+  Note: The shorthand purposefully omits the 'text-underline-position' property,
   which is a language/writing-system–dependent setting that keys off the content,
   so that it can cascade and inherit independently
   from the (uninherited) stylistic settings of the 'text-decoration' shorthand.