Error in documentation for Xdp.Portal::session-state-changed

[lawmurray]

The documentation for Xdp.Portal::session-state-changed has the third argument of the callback function as a pointer, whereas it seems it should be a value:

void
session_state_changed (
  XdpPortal* self,
  gboolean screensaver_active,
  XdpLoginSessionState* session_state,
  gpointer user_data
)

i.e. I think XdpLoginSessionStage* session_state should be XdpLoginSessionStage session_state there. I couldn't work out how this comes about in the documentation generation process to submit a PR though, sorry.