Fixed go install usage

[hsbt]

Hi, the current instruction is failed like:

$ go install -u github.com/DarthSim/overmind/v2
flag provided but not defined: -u
usage: go install [build flags] [packages]
Run 'go help install' for details.

I fixed it to correct usage of go install.

[DarthSim]

Hi @hsbt!
Thank's for your contribution!
I changed github.com/DarthSim/overmind@v2 back to github.com/DarthSim/overmind/v2 as github.com/DarthSim/overmind@v2 installs an old version

[hsbt]

Thanks. But the current instruction is also not working.

$ go install github.com/DarthSim/overmind/v2
go: 'go install' requires a version when current directory is not in a module

It should be:

go install github.com/DarthSim/overmind/v2@latest