libwebsockets: 2.4.1 -> 2.4.2

Semi-automatic update generated by https://github.com/ryantm/nix-update tools. 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 2.4.2 with grep in /nix/store/y3zmgw1wy80xwfmjx8d97nvrr5qfzrmp-libwebsockets-2.4.2
- found 2.4.2 in filename of file in /nix/store/y3zmgw1wy80xwfmjx8d97nvrr5qfzrmp-libwebsockets-2.4.2