kotlin: 1.2.31 -> 1.2.40

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

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

These checks were done:

- built on NixOS
- ran ‘/nix/store/w1k17lqv3cc8sszxnmzg8g6lcc1pxkk8-kotlin-1.2.40/bin/kotlin -h’ got 0 exit code
- ran ‘/nix/store/w1k17lqv3cc8sszxnmzg8g6lcc1pxkk8-kotlin-1.2.40/bin/.kotlin-wrapped -h’ got 0 exit code
- found 1.2.40 with grep in /nix/store/w1k17lqv3cc8sszxnmzg8g6lcc1pxkk8-kotlin-1.2.40
- directory tree listing: https://gist.github.com/886158de7b36d9a61fcbc13d2638779a