Disentangle images loading on-demand from scripting

Closes #5445, and aligns with implementations.

Author: domenic

source

@@ -27277,18 +27277,9 @@ was an English &lt;a href="/wiki/Music_hall">music hall&lt;/a> singer, ...</code
 
   <h6>When to obtain images</h6>
 
-  <p>For <code>img</code> elements whose <span>relevant settings object</span> has <span
-  data-x="concept-environment-noscript">scripting disabled</span>, user agents may obtain the image
-  immediately or on demand. For <code>img</code> elements whose <span>relevant settings
-  object</span> has <span data-x="concept-environment-script">scripting enabled</span>, user agents
-  must obtain the image immediately.</p>
-
-  <p class="note">These requirements are phrased in terms of <span
-  data-x="concept-environment-script">scripting being enabled</span> for the <span>relevant settings
-  object</span>, instead of in terms of <span data-x="concept-n-script">scripting being
-  enabled</span> for the <code>img</code> element itself, because it is important that images be
-  obtained immediately even when their <span>node document</span>'s <span
-  data-x="concept-document-bc">browsing context</span> is null.</p>
+  <p>By default, images are obtained immediately. User agents may provide users with the option to
+  instead obtain them on-demand. (The on-demand option might be used by bandwidth-constrained users,
+  for example.)</p>
 
   <p>When obtaining images immediately, the user agent must synchronously <span>update the image
   data</span> of the <code>img</code> element, with the <i>restart animation</i> flag set if so