fix(mu4e): remove stray +workspace-delete invokation

In commit 5289861109 `+workspace-delete` was
replaced by `+workspace-kill`.

The changes were not complete, though, and mu4e does not start anymore.

This patch completes the changes and should restore mu4e.

Amend: 5289861109

modules/email/mu4e/autoload/email.el

@@ -65,7 +65,7 @@ default/fallback account."
       ;; as otherwise you can accumulate empty workspaces
       (progn
         (unless (+workspace-buffer-list)
-          (+workspace-delete (+workspace-current-name)))
+          (+workspace-kill (+workspace-current-name)))
         (+workspace-switch +mu4e-workspace-name t))
     (setq +mu4e--old-wconf (current-window-configuration))
     (delete-other-windows)