Fix Grid T+T link in indexcontent.html
A previous commit changed the file name for the Grid Track and Trace Family
Specification, but did not change the "pathto" name in the landing page.
This commit fixes the problem.
<h1>Hyperledger Grid documentation</h1>
- <p class="biglink"><a class="biglink" href="{{ pathto("family_specification") }}">{% trans %}Grid Track and Trace Transaction Family Specification{% endtrans %}</a><br/>
+ <p class="biglink"><a class="biglink" href="{{ pathto("grid_track_and_trace_family_specification") }}">{% trans %}Grid Track and Trace Transaction Family Specification{% endtrans %}</a><br/>
<span class="linkdescr">{% trans %}learn about Grid Track and Trace{% endtrans %}</span></p>
<p class="biglink"><a class="biglink" href="{{ pathto("contents") }}">{% trans %}Table of Contents{% endtrans %}</a><br/>
