event-loop: do not set CA_COMMAND_BUSY #9853

CA_COMMAND_BUSY in nv_event() was carried over from Vim nv_cursorhold()
(ref: e5165bae11). It prevents :startinsert from working during a RPC
call, so remove it.

Helped-by: glacambre <me@r4>
closes #7254

src/nvim/normal.c

@@ -8001,7 +8001,6 @@ static void nv_event(cmdarg_T *cap)
   // lists or dicts being used.
   may_garbage_collect = false;
   multiqueue_process_events(main_loop.events);
-  cap->retval |= CA_COMMAND_BUSY;       // don't call edit() now
   finish_op = false;
 }