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

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

These checks were done:

- built on NixOS
- Warning: no invocation of /nix/store/2ig3b399yp3nlnhfyrv6yypyaf7x7rk3-flatpak-0.99.2/bin/flatpak-bisect had a zero exit code or showed the expected version
- /nix/store/2ig3b399yp3nlnhfyrv6yypyaf7x7rk3-flatpak-0.99.2/bin/flatpak-coredumpctl passed the binary check.
- /nix/store/2ig3b399yp3nlnhfyrv6yypyaf7x7rk3-flatpak-0.99.2/bin/.flatpak-wrapped passed the binary check.
- /nix/store/2ig3b399yp3nlnhfyrv6yypyaf7x7rk3-flatpak-0.99.2/bin/flatpak passed the binary check.
- 3 of 4 passed binary check by having a zero exit code.
- 2 of 4 passed binary check by having the new version present in output.
- found 0.99.2 with grep in /nix/store/2ig3b399yp3nlnhfyrv6yypyaf7x7rk3-flatpak-0.99.2
- directory tree listing: https://gist.github.com/4cd5330783ac4dc304e7ceba12395ba0
- du listing: https://gist.github.com/81060efb0965f7e05ba54655bce0f2ca

flatpak: 0.99.1 -> 0.99.2