Editorial: remove some copypasta around CORS settings attribute

Author: annevk

source

@@ -7320,8 +7320,8 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
 
   <h4>CORS settings attributes</h4>
 
-  <p>A <dfn>CORS settings attribute</dfn> The attribute is an <span>enumerated attribute</span> with
-  the following keywords and states:</p>
+  <p>A <dfn>CORS settings attribute</dfn> is an <span>enumerated attribute</span> with the following
+  keywords and states:</p>
 
   <table>
    <thead>