Editorial: tone down X-Frame-Options obsoletion message

Fixes whatwg#10936.

Author: tunetheweb

source

@@ -106418,10 +106418,10 @@ new PaymentRequest(…); // Allowed to use
 
   <h3>The `<code>X-Frame-Options</code>` header</h3>
 
-  <p>The `<dfn http-header><code>X-Frame-Options</code></dfn>` HTTP response header is a legacy way
+  <p>The `<dfn http-header><code>X-Frame-Options</code></dfn>` HTTP response header is a way
   of controlling whether and how a <code>Document</code> may be loaded inside of a <span>child
-  navigable</span>. It is obsoleted by the <code data-x="frame-ancestors
-  directive">frame-ancestors</code> CSP directive, which provides more granular control over the
+  navigable</span>. For sites using CSP, the <code data-x="frame-ancestors
+  directive">frame-ancestors</code> directive provides more granular control over the
   same situations. It was originally defined in <cite>HTTP Header Field X-Frame-Options</cite>, but
   the definition<span w-nodev> and processing model</span> here supersedes that document.
   <ref>CSP</ref> <ref>RFC7034</ref>