Improve synapse-admin reverse-proxying fix

Fixup for 6a31fba346

roles/custom/matrix-synapse-admin/tasks/inject_into_nginx_proxy.yml

@@ -30,8 +30,9 @@
           See: https://github.com/Awesome-Technologies/synapse-admin/issues/322
         #}
         sub_filter_once off;
-        sub_filter_types text/css;
         sub_filter "/static/" "{{ matrix_synapse_admin_public_endpoint }}/static/";
+        sub_filter "/favicon.ico" "{{ matrix_synapse_admin_public_endpoint }}/favicon.ico";
+        sub_filter "/manifest.json" "{{ matrix_synapse_admin_public_endpoint }}/manifest.json";
       }
 
 - name: Register Synapse Admin proxying configuration with matrix-nginx-proxy