Update the maximum number of the detected spots to catch horizontal shift.

mcs Actor has the maximum number of the detected spot to use further process:

https://github.com/Subaru-PFS/ics_mcsActor/blob/f093b87951034449e5cefa0db27e26f11776c1ea/python/mcsActor/Commands/McsCmd.py#L1677

The current number is 5000, but it doesn't catch the horizontal shift (INSTRM-2693) as the number of the spots mostly just doubled (i.e., ~4800 or so). In addition, the above seems to use just the first 5000 or so, which is not necessarily the correct spots. 

Handling the maximum number of spots could be optimized.