Fix additional reference for site_name

Applies to https://github.com/netbootxyz/netboot.xyz/issues/1095

roles/netbootxyz/templates/index.html.j2

@@ -54,7 +54,7 @@ exit
     </tr>
     {% endfor %}
   </table>
-  <p>Multiarch (x86_64 and arm64) Legacy and EFI Combined iPXE Bootloaders</p>
+  <p>Multi-arch (x86_64 and arm64) Legacy and EFI Combined iPXE Bootloaders</p>
   <table style="width:100%">
     <!-- table header -->
     <tr>
@@ -66,7 +66,7 @@ exit
     {% for item in bootloaders.multiarch %}
     <tr>
        <td> {{ item.type }} </td>
-       <td> <a href="ipxe/{{ site_name }}{{ item.output_bin }}">{{ site_name }}{{ item.output_bin }}</a> </td>
+       <td> <a href="ipxe/{{ bootloader_filename }}{{ item.output_bin }}">{{ bootloader_filename }}{{ item.output_bin }}</a> </td>
        <td> {{ item.desc }} </td>
     </tr>
     {% endfor %}