Use new PGM server guide link

[TheRealPear]

I noticed that MCResourcepile still links to the RUNNING.MD file for server setup. I've opened this pull request as I think the link to PGM Docs would be far more helpful for new and advanced users alike, as it goes in more depth about setting up a SportPaper server with PGM.

[mitchts]

I don't think this environment blurb is actually used anywhere since the PGM page was redesigned.

What needs to be updated is the "body" of data/maps/pgm.json.

[mitchts]

Thank you!