[RRFC] bare `npm unlink` should work

[ljharb]

Motivation ("The Why")

npm link works.

npm unlink doesn't.

Example

$ npm unlink
npm ERR! Must provide a package name to remove

npm ERR! A complete log of this run can be found in:
npm ERR!     $HOME/.npm/_logs/2022-04-21T16_17_37_636Z-debug-0.log

Seems pretty straightforward to me - if i can npm foo i should be able to npm unfoo.