Fix srcset attribute guidelines

Conformance requirement for the width descriptor is about the sizes attribute, not the srcset attribute.

Fixes whatwg#3250.

source

@@ -27097,7 +27097,7 @@ was an English &lt;a href="/wiki/Music_hall">music hall&lt;/a> singer, ...</code
   must match the <span>intrinsic width</span> in the resource given by the
   <span>image candidate string</span>'s URL, if it has an <span>intrinsic width</span>.</p>
 
-  <p>If an element has a <span>srcset attribute</span> present, all <span data-x="image
+  <p>If an element has a <span>sizes attribute</span> present, all <span data-x="image
   candidate string">image candidate strings</span> for that element must have the <span>width
   descriptor</span> specified.</p>
 
@@ -121861,6 +121861,7 @@ INSERT INTERFACES HERE
   Joel Spolsky,
   Joel Verhagen,
   Johan Herland,
+  Johanna Herman,
   John Boyer,
   John Bussjaeger,
   John Carpenter,
@@ -122296,6 +122297,7 @@ INSERT INTERFACES HERE
   Travis Leithead,
   Trevor Rowbotham,
   Trevor Saunders,
+  Trey Eckels,
   triple-underscore, <!-- GitHub -->
   Tyler Close,
   Valentin Gosu,