Update @@foo symbol notation to %Symbol.foo% notation

Follows tc39/ecma262#1314.

source

@@ -2951,10 +2951,10 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
      <li><dfn data-x-href="https://tc39.es/ecma262/#sec-abstract-closure">abstract closure</dfn></li>
      <li><dfn data-x-href="https://tc39.es/ecma262/#immutable-prototype-exotic-object">immutable prototype exotic object</dfn></li>
      <li><dfn data-x-href="https://tc39.es/ecma262/#sec-well-known-symbols">Well-Known Symbols</dfn>, including
-         <dfn>@@hasInstance</dfn>,
-         <dfn>@@isConcatSpreadable</dfn>,
-         <dfn>@@toPrimitive</dfn>, and
-         <dfn>@@toStringTag</dfn></li>
+         <dfn>%Symbol.hasInstance%</dfn>,
+         <dfn>%Symbol.isConcatSpreadable%</dfn>,
+         <dfn>%Symbol.toPrimitive%</dfn>, and
+         <dfn>%Symbol.toStringTag%</dfn></li>
      <li><dfn data-x-href="https://tc39.es/ecma262/#sec-well-known-intrinsic-objects">Well-Known Intrinsic Objects</dfn>, including
          <dfn data-x-href="https://tc39.es/ecma262/#sec-properties-of-the-array-prototype-object">%Array.prototype%</dfn>,
          <dfn data-x-href="https://tc39.es/ecma262/#sec-properties-of-the-error-prototype-object">%Error.prototype%</dfn>,
@@ -88729,8 +88729,8 @@ dictionary <dfn dictionary>DragEventInit</dfn> : <span>MouseEventInit</span> {
   <h6><dfn>CrossOriginPropertyFallback</dfn> ( <var>P</var> )</h6>
 
   <ol>
-   <li><p>If <var>P</var> is "<code data-x="">then</code>", <span>@@toStringTag</span>,
-   <span>@@hasInstance</span>, or <span>@@isConcatSpreadable</span>, then return
+   <li><p>If <var>P</var> is "<code data-x="">then</code>", <span>%Symbol.toStringTag%</span>,
+   <span>%Symbol.hasInstance%</span>, or <span>%Symbol.isConcatSpreadable%</span>, then return
    <span>PropertyDescriptor</span>{
    [[Value]]: undefined,
    [[Writable]]: false,
@@ -88908,7 +88908,7 @@ dictionary <dfn dictionary>DragEventInit</dfn> : <span>MouseEventInit</span> {
    data-x="list append">append</span> <var>e</var>.[[Property]] to <var>keys</var>.</p></li>
 
    <li><p>Return the concatenation of <var>keys</var> and « "<code data-x="">then</code>",
-   <span>@@toStringTag</span>, <span>@@hasInstance</span>, <span>@@isConcatSpreadable</span>
+   <span>%Symbol.toStringTag%</span>, <span>%Symbol.hasInstance%</span>, <span>%Symbol.isConcatSpreadable%</span>
    ».</p></li>
   </ol>
 
@@ -90412,7 +90412,7 @@ interface <dfn interface>BarProp</dfn> {
    [[Enumerable]]: false,
    [[Configurable]]: false }).</p></li>
 
-   <li><p>Perform ! <var>location</var>.[[DefineOwnProperty]](<span>@@toPrimitive</span>, {
+   <li><p>Perform ! <var>location</var>.[[DefineOwnProperty]](<span>%Symbol.toPrimitive%</span>, {
    [[Value]]: undefined,
    [[Writable]]: false,
    [[Enumerable]]: false,
@@ -90424,12 +90424,12 @@ interface <dfn interface>BarProp</dfn> {
    <li><p>Return <var>location</var>.</p></li>
   </ol>
 
-  <p class="note">The addition of <code data-x="">valueOf</code> and <span>@@toPrimitive</span> own
+  <p class="note">The addition of <code data-x="">valueOf</code> and <span>%Symbol.toPrimitive%</span> own
   data properties, as well as the fact that all of <code>Location</code>'s IDL attributes are marked
   <code data-x="">[<span>LegacyUnforgeable</span>]</code>, is required by legacy code that consulted
   the <code>Location</code> interface, or stringified it, to determine the <span
   data-x="concept-document-url">document URL</span>, and then used it in a security-sensitive way.
-  In particular, the <code data-x="">valueOf</code>, <span>@@toPrimitive</span>, and <code
+  In particular, the <code data-x="">valueOf</code>, <span>%Symbol.toPrimitive%</span>, and <code
   data-x="">[<span>LegacyUnforgeable</span>]</code> stringifier mitigations ensure that code such as
   <code data-x="">foo[location] = bar</code> or <code data-x="">location + ""</code> cannot be
   misdirected.</p>