Update to use navigables instead of browsing contexts

Follows whatwg/html#6315. One reference remains to "target browsing context" which probably requires HTML-side updates first.

Author: domenic

fetch.bs

@@ -1726,9 +1726,8 @@ not always relevant and might require different behavior.
  submission algorithm.
 
  <p>CSP will also need to check <a for=/>request</a>'s <a for=request>client</a>'s
- <a for="environment settings object">global object</a>'s
- <a for=Window>browsing context</a>'s <a>ancestor browsing contexts</a> for various CSP
- directives.
+ <a for="environment settings object">global object</a>'s <a>associated <code>Document</code></a>'s
+ <a for=Document>ancestor navigables</a> for various CSP directives.
 </div>
 
 <hr>
@@ -6187,7 +6186,7 @@ agent's <a>CORS-preflight cache</a> for which there is a <a>cache entry match</a
   <var>request</var>'s <a for=request>current URL</a>'s <a for=url>origin</a> is not
   <a>same origin</a> with <var>request</var>'s <a for=request>origin</a>, then return failure.
 
-  <p class=note>This is necessary for navigations of a nested browsing context. There,
+  <p class=note>This is necessary for navigations of a nested navigable. There,
   <var>request</var>'s <a for=request>origin</a> would be the container document's
   <a for=Document>origin</a> and the <a>TAO check</a> would return failure. Since navigation timing
   never validates the results of the <a>TAO check</a>, the nested document would still have access