citrix_workspace_19_8_0: fix url

When a new version of the Citrix workspace app is released, there's no
versioned URL available. This means that as soon as a new version is
released, the homepage needs to be altered to ensure that the error
message from `requireFile` points to the proper download URL.

(cherry picked from commit 518b5ef)

pkgs/applications/networking/remote/citrix-workspace/default.nix

@@ -59,7 +59,7 @@ let
         x86hash   = "0afcqirb4q349r3izy88vqkszg6y2wg14iwypk6nrmvwgvcl6jdn";
         x64suffix = "20";
         x86suffix = "20";
-        homepage  = https://www.citrix.com/downloads/workspace-app/linux/workspace-app-for-linux-latest.html;
+        homepage  = https://www.citrix.com/downloads/workspace-app/legacy-workspace-app-for-linux/workspace-app-for-linux-1908.html;
       };
     };