minor fixes

Fixes: whatwg#1283

fetch.bs

@@ -5147,7 +5147,7 @@ optional boolean <var>forceNewConnection</var> (default false), run these steps:
  <li><p>Let <var>timingInfo</var> be <var>fetchParams</var>'s <a for="fetch params">timing info</a>.
 
  <li><p>Let <var>httpCache</var> be the result of <a>determining the HTTP cache partition</a>, given
- <var>httpRequest</var>.
+ <var>request</var>.
 
  <li><p>If <var>httpCache</var> is null, then set <var>request</var>'s <a for=request>cache mode</a>
  to "<code>no-store</code>".
@@ -5993,7 +5993,7 @@ new Headers(meta2);
   <var>object</var>:
 
   <ol>
-   <li><p>If <var>header</var> does not contain exactly two items, then <a>throw</a> a
+   <li><p>If <var>header</var> is not a <a>sequence</a> which contains exactly two items, then <a>throw</a> a
    {{TypeError}}.
 
    <li><p><a lt=append for=Headers>Append</a> <var>header</var>'s first item/<var>header</var>'s