make dok: don't run tidy on the docbook generated html

make dok: don't run tidy on the docbook generated html

at least as of tidy 5.6.0, tidy -indent -wrap
breaks <pre> formatting if the line is wrapped

<pre>a long line
</pre>

when indented and wrapped ends up like this
      <pre>
      a long line
</pre>

The pre-formatted text shouldn't have leading spaces added.  It should look like
      <pre>
a long line
</pre>