Fix the empty netmon description in the help message

[amete]

Hi @graeme-a-stewart,

I noticed that the description for netmon in the help message is empty:

Monitors available:
 - countmon : Monitor number of processes and threads
 - cpumon : Monitor cpu time used
 - iomon : Monitor input and output activity
 - memmon : Monitor memory usage
 - nvidiamon : Monitor NVIDIA GPU activity
 - wallmon : Monitor wallclock time
 - netmon : 

More information: https://github.com/HSF/prmon

This PR should fix it:

Monitors available:
 - countmon : Monitor number of processes and threads
 - cpumon : Monitor cpu time used
 - iomon : Monitor input and output activity
 - memmon : Monitor memory usage
 - nvidiamon : Monitor NVIDIA GPU activity
 - wallmon : Monitor wallclock time
 - netmon : Monitor network activity (device level)

More information: https://github.com/HSF/prmon

Please let me know what you think, many thanks.

Best,
Serhan

[graeme-a-stewart]

Well spotted @amete. I really do hate these templated monitor codes, however, it seems to be a necessary evil in C++!

[graeme-a-stewart]

Sorry, I overlooked this for so long!

[amete]

No worries @graeme-a-stewart, it's a minor thing in any case, thanks a lot 😄