Fix speculative script fetching to be based on connectedness

Using "inserted into the document" is not correct, as that's not what governs (regular) script fetching.

source

@@ -62555,16 +62555,15 @@ o............A....e
 
       <p>For performance reasons, user agents may start fetching the classic script or module graph
       (as defined above) as soon as the <code data-x="attr-script-src">src</code> attribute is set,
-      instead, in the hope that <var>el</var> will be inserted into the document (and that the
-      <code data-x="attr-script-crossorigin">crossorigin</code> attribute won't change value in the
-      meantime). Either way, once <var>el</var> is <span data-x="node is inserted into a
-      document">inserted into the document</span>, the load must have started as described in this
-      step. If the UA performs such prefetching, but <var>el</var> is never inserted in the
-      document, or the <code data-x="attr-script-src">src</code> attribute is dynamically
-      changed,<!-- or the base URL is dynamically changed,--> or the <code
-      data-x="attr-script-crossorigin">crossorigin</code> attribute is dynamically changed, then
-      the user agent will not execute the script so obtained, and the fetching process will have
-      been effectively wasted.</p>
+      instead, in the hope that <var>el</var> will become connected (and that the <code
+      data-x="attr-script-crossorigin">crossorigin</code> attribute won't change value in the
+      meantime). Either way, once <var>el</var> <span>becomes connected</span>, the load must have
+      started as described in this step. If the UA performs such prefetching, but <var>el</var>
+      never becomes connected, or the <code data-x="attr-script-src">src</code> attribute is
+      dynamically changed, <!-- or the base URL is dynamically changed,--> or the <code
+      data-x="attr-script-crossorigin">crossorigin</code> attribute is dynamically changed, then the
+      user agent will not execute the script so obtained, and the fetching process will have been
+      effectively wasted.</p>
      </li>
     </ol>
    </li>