Removes defunct community links

[robacarp]

Several of these have been inactive for 3+ years. I think having links to defunct community projects makes crystal a bit bruised.

[Blacksmoke16]

Technically the gitter one is still valid. But would also be open to updating it to its new URL vs having it redirect. I feel like the IRC one is still technically also valid even if it's not all that active. NVM, IRC is now ircs://irc.libera.chat:6697#crystal-lang, so maybe should update that one too.

[robacarp]

I'm on the IRC channel still, and it's essentially a desert. Once a week someone joins and asks "is this still active?" and nobody responds for an hour and they give up and go elsewhere. I'm an IRC enthusiast as any, but I haven't had a real conversation on there in a long time despite being logged into it daily.

Since Discord is where live chat actually happens, it would probably be best to put a non-expiring invite link to the discord -- I think an admin needs to generate that link. Is that a good addition?

I guess I didn't realize it, but it does seem like gitter is still far more active than I remembered it being.

[Blacksmoke16]

Even so, while it's still listed officially on https://crystal-lang.org/community/#chat, it makes sense to keep it 🤷. Guess it does bring up the question of whether it should still be considered an official chat room tho.

[robacarp]

Good point. I see the Discord server is in the "unofficial" section. I'll leave the debate about what is considered official and unofficial to the community management ;-)