Removed all insights-related code (#393)

Co-authored-by: pikachu0542 <112343747+pikachu0542@users.noreply.github.com>
Co-authored-by: Shaela Spring <shaeespring@gmail.com>

Author: 3 people

_includes/nav.html

@@ -30,7 +30,6 @@
                         <li><a {% if page.active == 'membership' %}class="active"{% endif %} href="/membership/">Overview</a></li>
                         <li><a {% if page.active == 'membership-intro' %}class="active"{% endif %} href="/membership/intro-process.html">New Members</a></li>
                         <li><a {% if page.active == 'membership-traditions' %}class="active"{% endif %} href="/membership/traditions.html">Traditions</a></li>
-                        <!--<li><a {% if page.active == 'membership-insights' %}class="active"{% endif %} href="/membership/insights.html">Insights</a></li>-->
                     </ul>
                 </li>
                 <li class="nav-item"><a {% if page.active == 'blog' %}class="active"{% endif %} href="/blog/">Blog</a></li>

_sass/_insights.scss

@@ -212,7 +212,6 @@ a.btn {
 @import "post";
 @import "eboard";
 @import "tour";
-@import "insights";
 @import "footer";
 @import "hackathon";
 @import "triple_image";