insomnia: 5.14.9 -> 5.15.0 (#38554)

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

This update was made based on information from https://repology.org/metapackage/insomnia/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 5.15.0 with grep in /nix/store/x52qaj81hs0q30360p9cr4zp0wq1cjcp-insomnia-5.15.0
- directory tree listing: https://gist.github.com/cb32b3e7392a6724e0a30657b52b3f26