Fix polybar hardcoding

Polybar restarting is now done through its provided ipc interface,
instead of relying on a hardcoded script on the system.

Previously, the system needed access to a `polybar-launch` script.
Now, it invokes the `polybar-msg` command which is provided by polybar
itself.

It is important that polybar has ipc enabled in its configuration for
the restart to work.

theme_xresources

@@ -43,8 +43,8 @@ theme() {
 #  Some applications reading from Xresources need a restart
 #  to use the new settings.
 theme_post() {
-  type polybar-launch >/dev/null 2>&1 && {
-    polybar-launch simple-top >/dev/null
+  type polybar-msg >/dev/null 2>&1 && {
+    polybar-msg cmd restart
     dbg_msg $app "Restarting polybar"
   }
 }