Update fetch.bs

Co-authored-by: Anne van Kesteren <[email protected]>

Author: sadym-chromium

fetch.bs

@@ -5891,7 +5891,7 @@ run these steps:
 
    <li>
     <p>If <var>httpRequest</var>'s <a for=request>header list</a> <a for="header list">does not
-    contain</a> `<code>User-Agent</code>`, then:
+    contain</a> `<code>User-Agent</code>`:
 
     <ol>
      <li><p>Let <var>userAgent</var> be the result of running the <a>WebDriver BiDi emulated