refactor!: remove deprecated plugins

BREAKING CHANGE: the following deprecated plugins have been removed:
`cargo`, `copydir`, `npx`, `osx`, and `rustup`. See the wiki for more info:
https://github.com/ohmyzsh/ohmyzsh/wiki/Plugins#removed

refactor(rustup)!: remove deprecated plugin

BREAKING CHANGE: the plugin was deprecated and is now removed. See the wiki for more info:
https://github.com/ohmyzsh/ohmyzsh/wiki/Plugins#removed