refactor(portal): Update 500 error page (#8420)

Why:

* This commit updates the 500 error page in the portal to have the same
look and feel of the 404 error page in order to be consistent within the
portal UI.

elixir/apps/web/lib/web/controllers/error_html/500.html.heex

@@ -30,7 +30,10 @@
     <div class="flex items-center h-screen p-16 bg-gray-50">
       <div class="container mx-auto flex flex-col items-center">
         <div class="flex flex-col gap-6 max-w-md text-center">
-          <img src={~p"/images/http-500.png"} class="h-auto max-w-full" alt="500 Error" />
+          <img src={~p"/images/logo.svg"} class="mr-5 h-32" alt="Firezone Logo" />
+          <h2 class="font-extrabold text-9xl text-primary-600">
+            <span class="sr-only">Error</span>500
+          </h2>
 
           <p class="text-2xl md:text-3xl">
             Something went wrong. We've already been notified and will get it fixed as soon as possible.