[contributing] Remove twitter link

Author: fabiencastan

view/contributing.html

@@ -35,7 +35,6 @@ <h1 style="margin-bottom: 10px;margin-top: 40px;">Follow us</h1>
                 <h4 class="text-center">
           		<a href="https://groups.google.com/forum/#!forum/alicevision" target="_blank" title="Mailing List"><i class="fas fa-3x fa-comments text-muted m-2" style="vertical-align:middle;"></i></a>
                 <a href="https://sketchfab.com/AliceVision" target="_blank" title="Sketchfab"><img src="img/logos/sketchfab_grey.png" style="width:68px;height:68px;opacity:1;vertical-align:middle;margin-left: 5px;margin-right: 5px"></a>
-                <a href="https://twitter.com/alicevision_org" target="_blank" title="Twitter"><i class="fab fa-3x fa-twitter text-muted m-2" style="vertical-align:middle;">&nbsp;&nbsp;</i></a>
                 <a href="https://www.linkedin.com/company/106541644" target="_blank" title="Linkedin"><i class="fab fa-3x fa-linkedin text-muted m-2" style="vertical-align:middle;">&nbsp;&nbsp;</i></a>
                 <a href="https://www.youtube.com/c/AliceVisionOrg" target="_blank" title="Youtube"><i class="fab fa-3x fa-youtube text-muted m-2" style="vertical-align:middle;">&nbsp;&nbsp;</i></a>
                 </h4>