[css-text-3] Fix typo

Author: fantasai

css-text-3/Overview.bs

@@ -688,7 +688,7 @@ Order of Operations</h4>
     <p>When multiple values are specified and therefore multiple transformations need to be applied,
       they are applied in the following order:
     <ol>
-      <li>''capitalize'', ''upercase'', and ''lowercase''
+      <li>''capitalize'', ''uppercase'', and ''lowercase''
       <li>''full-width''
       <li>''full-size-kana''
     </ol>