[css-text-decor-3] Fix HTML5 validation error.

Author: fantasai

css-text-decor-3/Overview.bs

@@ -776,7 +776,7 @@ Emphasis Mark Position: the 'text-emphasis-position' property</h3>
 			</thead>
 			<tbody>
 				<tr>
-					<td scope="row">Japanese
+					<th scope="row">Japanese
 					<td rowspan="3">over
 					<td rowspan="3">right
 					<td rowspan="3">
@@ -789,11 +789,11 @@ Emphasis Mark Position: the 'text-emphasis-position' property</h3>
 						     title="Emphasis applied on the right of a fragment of Japanese text"
 						     src="images/text-emphasis-v.gif" height="79" width="34">
 				<tr>
-					<td scope="row">Korean
+					<th scope="row">Korean
 				<tr>
-					<td scope="row">Mongolian
+					<th scope="row">Mongolian
 				<tr>
-					<td scope="row">Chinese
+					<th scope="row">Chinese
 					<td>under
 					<td>right
 					<td>