fixed Icons

Signed-off-by: Jacob Haight <70984053+some45bucks@users.noreply.github.com>

Author: some45bucks

index.html

@@ -75,7 +75,7 @@ <h1 class="title is-1 publication-title">Realistic Heterogeneous Multi-Agent RL
                     <div class="publication-links">
                         <span class="link-block">
                             <a href="https://arxiv.org/pdf/YOUR_PAPER_ID.pdf" class="external-link button is-normal is-rounded is-dark">
-                                <span class="icon"><i class="fa fa-file-pdf"></i></span>
+                                <span class="icon"><i class="fa fa-file-pdf-o"></i></span>
                                 <span>Paper</span>
                             </a>
                         </span>