Update Checkport references

[n0rs3]

Updated the references to checkport in the is_port_open comments.

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Hello @theCalcaholic, it's been a while since we last spoke, how are you? 😄 (I changed my username on GitHub from ZendaiOwl to n0rs3)

I'm making this pull request to update the references in the comments to point to where I have the repository now.

[theCalcaholic]

Hey @n0rs3 , nice to hear from you :)
Thank you for the update.
I'm not too comfortable with hosting the port check somewhere where it may cause you expenses, though.
I'll move it to my own server soon, if you don't mind.
I'd set it up so it automatically pulls your docker image once per day, so you could still easily push updates.

[n0rs3]

If you rather want to host it yourself that's okay with me, I also have no issue to keep running it :)

It's not gotten close to hitting the limits in the past 2 years it's been running so I'm not particularly worried. The limit is over 430 simultaneous request per seconds for an entire month after all. The text is mostly to discourage frivolous use outside the admin panel.

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How are things with you otherwise?

I finally graduated in march :D