drop golint

[mcandre]

golint has an outstanding problem with generating spurious warnings, when //go:generate... lines are used atop of package declarations. It may even trigger for build tags as well.

Regardless, golint is now archived. The author recommends using staticcheck instead.

Update:

• [x] mage extras
• [x] buttery
• [x] mcandre/linters
• [x] various go projects
• [x] octane