kotlin: 1.2.30 -> 1.2.31

Semi-automatic update generated by https://github.com/ryantm/nix-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/c8gxcm1qd27rc1q7m164vwys12rr7kzj-kotlin-1.2.31/bin/kotlin -h` got 0 exit code
- ran `/nix/store/c8gxcm1qd27rc1q7m164vwys12rr7kzj-kotlin-1.2.31/bin/kotlin-dce-js -h` got 0 exit code
- ran `/nix/store/c8gxcm1qd27rc1q7m164vwys12rr7kzj-kotlin-1.2.31/bin/kotlinc -h` got 0 exit code
- ran `/nix/store/c8gxcm1qd27rc1q7m164vwys12rr7kzj-kotlin-1.2.31/bin/kotlinc-js -h` got 0 exit code
- ran `/nix/store/c8gxcm1qd27rc1q7m164vwys12rr7kzj-kotlin-1.2.31/bin/kotlinc-jvm -h` got 0 exit code
- ran `/nix/store/c8gxcm1qd27rc1q7m164vwys12rr7kzj-kotlin-1.2.31/bin/.kotlin-wrapped -h` got 0 exit code
- ran `/nix/store/c8gxcm1qd27rc1q7m164vwys12rr7kzj-kotlin-1.2.31/bin/.kotlin-dce-js-wrapped -h` got 0 exit code
- ran `/nix/store/c8gxcm1qd27rc1q7m164vwys12rr7kzj-kotlin-1.2.31/bin/.kotlinc-js-wrapped -h` got 0 exit code
- ran `/nix/store/c8gxcm1qd27rc1q7m164vwys12rr7kzj-kotlin-1.2.31/bin/.kotlinc-jvm-wrapped -h` got 0 exit code
- found 1.2.31 with grep in /nix/store/c8gxcm1qd27rc1q7m164vwys12rr7kzj-kotlin-1.2.31
- directory tree listing: https://gist.github.com/2abc86ffb8a29b93e0ee8cdc45c72125