Revert "nixos/display-managers: install sessionData.desktops"

This reverts commit 3cd2b59b8c.

It created infinite recursion when using LXQt, since lxqt module
uses `config.system.path` in `services.xserver.desktopManager.session`.
`config.system.path` is a `buildEnv` that depends on `environment.systemPackages`.

nixos/modules/services/x11/display-managers/default.nix

@@ -474,13 +474,6 @@ in
             )
             [dms wms]
           );
-
-    # Make xsessions and wayland sessions installed at
-    # /run/current-system/sw/share as some programs
-    # have behavior that depends on them being installed
-    environment.systemPackages = [
-      cfg.displayManager.sessionData.desktops
-    ];
   };
 
   imports = [