Drop repo's 'crystallang' topic

[matiasgarciaisaia]

The Crystal community has somewhat decided to use crystal as the language's topic.

To avoid fragmentation in the community, please drop the crystallang topic, that only has ~3 repositories at the moment. We're sticking to crystal, instead.

Any contributor can change it from the repo's homepage.

See crystal-lang/crystal#4241 for more context.

Thank you very much :)

[matiasgarciaisaia]

Friendly reminder about nuking the crystallang topic from orbit - this is the last remaining repo on that! :)