Fix PHP 7.3 regression in ?/users

This gets rid of the "Case-insensitive constants are deprecated" error
by passing doing |upper before passing to constant().

templates/mod/users.html

@@ -47,10 +47,10 @@
 				</td>
 			{% endif %}
 			<td>
-				{% if mod|hasPermission(config.mod.promoteusers) and user.type < constant(config.mod.groups[0:-1]|last) %}
+				{% if mod|hasPermission(config.mod.promoteusers) and user.type < constant(config.mod.groups[0:-1]|last|upper) %}
 					<a style="float:left;text-decoration:none" href="?/users/{{ user.id }}/promote/{{ user.promote_token }}" title="{% trans 'Promote' %}">&#9650;</a> 
 				{% endif %}
-				{% if mod|hasPermission(config.mod.promoteusers) and user.type > constant(config.mod.groups|first) %}
+				{% if mod|hasPermission(config.mod.promoteusers) and user.type > constant(config.mod.groups|first|upper) %}
 					<a style="float:left;text-decoration:none" href="?/users/{{ user.id }}/demote/{{ user.demote_token }}" title="{% trans 'Demote' %}"{% if mod.id == user.id %} onclick="return confirm('{% trans 'Are you sure you want to demote yourself?' %}')"{% endif %}>&#9660;</a> 
 				{% endif %}
 				{% if mod|hasPermission(config.mod.modlog) %}