Remove usage of top-bar-left class

We don't need it since it's only used for flexbox styles, and we
already have a `flex-grow` rule for the `h1` element which does the
same thing.

app/components/layout/admin_header_component.html.erb

@@ -18,14 +18,12 @@
     <% end %>
 
     <div class="top-bar">
-      <div class="top-bar-left">
       <h1>
         <%= link_to namespace_path do %>
           <%= setting["org_name"] %>
           <br><small><%= namespaced_header_title %></small>
         <% end %>
       </h1>
-      </div>
 
       <% if show_account_menu? %>
         <div id="responsive_menu">