restore full width (#3493)

During the bootstrap 5 update in 6878670 (#3455) this class was changed from
`content` to `container`. The `container` class, unlike `content`, has a max
width of 1320px. Restore prior behavior of using the full width by using
`container-fluid` to avoid wasted whitespace.

Author: q3aiml

app/views/layouts/rails_admin/application.html.erb

@@ -14,7 +14,7 @@
           <%= render "layouts/rails_admin/sidebar_navigation" %>
         </div>
         <div class="col-sm-9 col-sm-offset-3 col-md-10 col-md-offset-2">
-          <div class="container">
+          <div class="container-fluid">
             <%= render template: 'layouts/rails_admin/content' %>
           </div>
         </div>