[css-writing-modes] Fixed a validator issue (nested a tag)

Author: kojiishi

css-writing-modes/Overview.html

@@ -1357,8 +1357,8 @@ <h4 class="heading settled heading" data-level=5.1.2 id=vertical-orientations><s
   <p>
     <a data-biblio-type=normative data-link-type=biblio href=#utr50 title=utr50>[UTR50]</a> defines the <code>Vertical_Orientation</code> property
     for the default character orientation of mixed-orientation vertical text.
-    When <a class=property data-link-type=propdesc href=#propdef-text-orientation title=text-orientation>text-orientation</a> is <a class=css data-link-type=maybe href=#valuedef-mixed title=mixed>mixed</a>,
-    the UA must typeset a <a data-link-type=dfn href=#character title=character>character</a> <a href=#typeset-upright>upright</a>
+    To typeset a <a data-link-type=dfn href=#character title=character>character</a> when <a class=property data-link-type=propdesc href=#propdef-text-orientation title=text-orientation>text-orientation</a> is <a class=css data-link-type=maybe href=#valuedef-mixed title=mixed>mixed</a>,
+    the UA must <a href=#typeset-upright>typeset it upright</a>
     if its orientation property is <code>U</code>, <code>Tu</code>, or <code>Tr</code>;
     or <a href=#typeset-sideways>typeset it sideways</a> (90° clockwise from horizontal)
     if its orientation property is <code>R</code>.

css-writing-modes/Overview.src.html

@@ -1299,8 +1299,8 @@ <h4 id='vertical-orientations'>
   <p>
     [[!UTR50]] defines the <code>Vertical_Orientation</code> property
     for the default character orientation of mixed-orientation vertical text.
-    When 'text-orientation' is ''mixed'',
-    the UA must typeset a <i>character</i> <a href="#typeset-upright">upright</a>
+    To typeset a <i>character</i> when 'text-orientation' is ''mixed'',
+    the UA must <a href="#typeset-upright">typeset it upright</a>
     if its orientation property is <code>U</code>, <code>Tu</code>, or <code>Tr</code>;
     or <a href="#typeset-sideways">typeset it sideways</a> (90&deg; clockwise from horizontal)
     if its orientation property is <code>R</code>.