libuv: 1.19.2 -> 1.20.0

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/libuv/versions.

These checks were done:

- built on NixOS
- Warning: no binary found that responded to help or version flags. (This warning appears even if the package isn't expected to have binaries.)
- found 1.20.0 with grep in /nix/store/r6j9x782s7pl6a5055icynmzk1991imw-libuv-1.20.0
- directory tree listing: https://gist.github.com/cff77ff2c13f732c2027bb680a833c5e