Update Model-net-snmp.nmis to revert to OMK-8576 fix

[John-Firstwave]

I just wanted to add a test node on a new VM, and I added athena, and it come up as DEGRADED in opCharts and I wondered why? There has been a reversion of OMK-8576, Improve default setting for High Number of System Processes Doug edited Model-net-snmp.nmis and overwrote the new value of 375 with the old value of 200.

I have changed it back to 375.