Don't set $TZ

We don't need to set $TZ, because we have /etc/localtime.  In fact,
setting $TZ without $TZDIR doesn't work anymore since Glibc no longer
contains zone info.

modules/services/web-servers/apache-httpd/default.nix

@@ -618,7 +618,6 @@ in
 
         environment =
           { PHPRC = if enablePHP then phpIni else "";
-            TZ = config.time.timeZone;
           } // (listToAttrs (concatMap (svc: svc.globalEnvVars) allSubservices));
 
         preStart =