mercurial/templates/paper/filelogentry.tmpl

context: add missing b prefix

This fixes
  mercurial/context.py:593: SyntaxError: cannot mix bytes and nonbytes literals (context.py, line 593)
in Python 3.

 <tr>
  <td class="age">{date|rfc822date}</td>
  <td class="author">{author|person}</td>
  <td class="description">
   <a href="{url|urlescape}rev/{node|short}{sessionvars%urlparameter}">{desc|strip|firstline|escape|nonempty}</a>
   {alltags}{rename%filelogrename}
  </td>
 </tr>
 {if(patch, '<tr><td colspan="3">{diff}</td></tr>')}