synapse: 0.2.99.3 -> 0.2.99.4

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

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

These checks were done:

- built on NixOS
- ran ‘/nix/store/rz2wn4lpkdqhwyz0qk7g41j2ykqmsj1b-synapse-0.2.99.4/bin/synapse -h’ got 0 exit code
- ran ‘/nix/store/rz2wn4lpkdqhwyz0qk7g41j2ykqmsj1b-synapse-0.2.99.4/bin/synapse --help’ got 0 exit code
- found 0.2.99.4 with grep in /nix/store/rz2wn4lpkdqhwyz0qk7g41j2ykqmsj1b-synapse-0.2.99.4
- directory tree listing: https://gist.github.com/77e6334e3c147a4af2d15a9878e112eb