windowmanager: do not enable 'windowmanager.service' by default

this is useless with xbmc in fullscreen/standalone mode, as
xbmc window won't even appear in  managed clients list. also
it could cause issues like xbmc losing focus.

3rdparty addons that need windowmanager for fullscreen/alt-tab/etc
can start it via 'systemctl start windowmanager.service'

closes #2675

packages/x11/other/dwm/package.mk

@@ -42,7 +42,3 @@ make_target() {
 configure_target() {
   :
 }
-
-post_install() {
-  enable_service windowmanager.service
-}

packages/x11/other/ratpoison/package.mk

@@ -54,7 +54,3 @@ post_makeinstall_target() {
   mkdir -p $INSTALL/etc
     cp $PKG_DIR/config/ratpoisonrc $INSTALL/etc
 }
-
-post_install() {
-  enable_service windowmanager.service
-}