Editorial: fix popover attribute index entries

Fix the backlinks to the attribute definitions, which has the effect of causing the attribute definitions to show up in the input and button element definitions. (The newlines here are, unfortunately, important.)

Also make popovertarget use the same "ID*" value space as other ID-accepting elements, as noted in #9144 (comment).

source

@@ -136059,12 +136059,14 @@ interface <dfn interface>External</dfn> {
           "<code data-x="attr-popover-manual">manual</code>";
     <tr>
      <th> <code data-x="">popovertarget</code>
-     <td> <code>input</code>; <code>button</code>
+     <td> <code data-x="attr-popovertarget">input</code>;
+          <code data-x="attr-popovertarget">button</code>
      <td> Targets a popover element to toggle, show, or hide
-     <td> ID of the element to toggle, show or, hide
+     <td> <span data-x="concept-id">ID</span>*
     <tr>
      <th> <code data-x="">popovertargetaction</code>
-     <td> <code>input</code>; <code>button</code>
+     <td> <code data-x="attr-popovertargetaction">input</code>;
+          <code data-x="attr-popovertargetaction">button</code>
      <td> Indicates whether a targeted popover element is to be toggled, shown, or hidden
      <td> "<code data-x="attr-popovertargetaction-toggle">toggle</code>";
           "<code data-x="attr-popovertargetaction-show">show</code>";