[Docs] `--help`: consolidate some help output
[Docs] `--help`: consolidate some help output

PeterDaveHelloKitchen/nvm,PeterDaveHelloKitchen/nvm,PeterDaveHello/nvm,creationix/nvm,evocateur/nvm,ljharb/nvm,PeterDaveHello/nvm,ljharb/nvm,evocateur/nvm,creationix/nvm