Update error message for 500 page

Now includes a link to our Discord server and concrete actions for the user, if the problem persists

pydis_site/templates/500.html

@@ -21,7 +21,7 @@
         </div>
         <div class="content-box">
             <h1>500 — Internal Server Error</h1>
-            <p>Sorry, but something went wrong on our side of things.</p>
+            <p>Something went wrong at our end. Please try again shortly, or if the problem persists, please let us know <a href="https://discord.gg/python">on Discord</a>.</p>
         </div>
     </div>
 </body>