Update nixpkgs to version 1.2.1

[khjorth]

Thanks for making this great clipboard manager! Is there any chance we could get the package in nixpkgs bumped to the latest version at some point?

Thanks!

[magicquark]

There is a PR open in nixpkgs to do this. See NixOS/nixpkgs#484504.

[savedra1]

Hi @khjorth,

PR is in progress. Sorry about the delay.