Use nvm default install instructions instead of homebrew

[imomaliev]

==> Caveats
==> nvm
Please note that upstream has asked us to make explicit managing
nvm via Homebrew is unsupported by them and you should check any
problems against the standard nvm install method prior to reporting.

You should create NVM's working directory if it doesn't exist:

  mkdir ~/.nvm

Add the following to ~/.zshrc or your desired shell
configuration file:

  export NVM_DIR="$HOME/.nvm"
  [ -s "/usr/local/opt/nvm/nvm.sh" ] && . "/usr/local/opt/nvm/nvm.sh"  # This loads nvm
  [ -s "/usr/local/opt/nvm/etc/bash_completion.d/nvm" ] && . "/usr/local/opt/nvm/etc/bash_completion.d/nvm"  # This loads nvm bash_completion

You can set $NVM_DIR to any location, but leaving it unchanged from
/usr/local/opt/nvm will destroy any nvm-installed Node installations
upon upgrade/reinstall.

Type `nvm help` for further information.

Bash completion has been installed to:
  /usr/local/etc/bash_completion.d
~