tiff_metadata.html has invalid HTML structure: misplaced </thead> element

Currently tiff_metadata.html contains a misplaced </thead> element:

525 <th scope="col">Reference</th></tr>
526 <tr>
527 </thead>
528 <tbody>

</thead> must be placed after line 525 which contains </tr> element and thus closes the row.
<tr> element on the line 526 must be inside <tbody> which currently is on the line 528.

This issue was overlooked during code review for JDK-8225372.