Change <rp>'s content model to Text

Fixes #1689.

source

@@ -19984,7 +19984,7 @@ this specification: the <abbr>WHATWG</abbr> and the
    <dt><span data-x="concept-element-contexts">Contexts in which this element can be used</span>:</dt>
    <dd>As a child of a <code>ruby</code> element, either immediately before or immediately after an <code>rt</code> element.</dd>
    <dt><span data-x="concept-element-content-model">Content model</span>:</dt>
-   <dd><span>Phrasing content</span>.</dd>
+   <dd><span data-x="text content">Text</span>.</dd>
    <dt><span data-x="concept-element-attributes">Content attributes</span>:</dt>
    <dd><span>Global attributes</span></dd>
    <dt><span data-x="concept-element-dom">DOM interface</span>:</dt><!--TOPIC:DOM APIs-->
@@ -115415,7 +115415,7 @@ interface <dfn>External</dfn> {
      <td>Parenthesis for ruby annotation text</td>
      <td>none</td>
      <td><code>ruby</code></td>
-     <td><span data-x="Phrasing content">phrasing</span></td>
+     <td><span data-x="text content">text</span></td>
      <td><span data-x="global attributes">globals</span></td>
      <td><code>HTMLElement</code></td>
     </tr>