Prevent desktop.el from saving/restoring eglot--managed-mode

Prevent desktop.el from saving/restoring eglot--managed-mode

Although desktop.el compatibility is Emacs bughttps://github.com/joaotavora/eglot/issues/56407, the optimal
solution agreed to there is a bit more work than what I have time to
right now.  See e.g.
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=bug%2356407https://github.com/joaotavora/eglot/issues/68.  For
now, just use `with-eval-after-load'

* eglot.el (Hacks desktop): Add eglot--managed-mode to
desktop-minor-mode-handlers

GitHub-reference: fix https://github.com/joaotavora/eglot/issues/990