anki: 2.0.50 -> 2.0.51

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

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

These checks were done:

- built on NixOS
- ran `/nix/store/pc80xsrc6hc3xw5fibqhcd3xy2z6krj8-anki-2.0.51/bin/anki -h` got 0 exit code
- ran `/nix/store/pc80xsrc6hc3xw5fibqhcd3xy2z6krj8-anki-2.0.51/bin/anki --help` got 0 exit code
- ran `/nix/store/pc80xsrc6hc3xw5fibqhcd3xy2z6krj8-anki-2.0.51/bin/anki --version` and found version 2.0.51
- ran `/nix/store/pc80xsrc6hc3xw5fibqhcd3xy2z6krj8-anki-2.0.51/bin/..anki-wrapped-wrapped -h` got 0 exit code
- ran `/nix/store/pc80xsrc6hc3xw5fibqhcd3xy2z6krj8-anki-2.0.51/bin/..anki-wrapped-wrapped --help` got 0 exit code
- ran `/nix/store/pc80xsrc6hc3xw5fibqhcd3xy2z6krj8-anki-2.0.51/bin/..anki-wrapped-wrapped --version` and found version 2.0.51
- ran `/nix/store/pc80xsrc6hc3xw5fibqhcd3xy2z6krj8-anki-2.0.51/bin/.anki-wrapped -h` got 0 exit code
- ran `/nix/store/pc80xsrc6hc3xw5fibqhcd3xy2z6krj8-anki-2.0.51/bin/.anki-wrapped --help` got 0 exit code
- ran `/nix/store/pc80xsrc6hc3xw5fibqhcd3xy2z6krj8-anki-2.0.51/bin/.anki-wrapped --version` and found version 2.0.51
- found 2.0.51 with grep in /nix/store/pc80xsrc6hc3xw5fibqhcd3xy2z6krj8-anki-2.0.51
- directory tree listing: https://gist.github.com/47b6928b65d620f470e7c7f117898265