focuswriter: 1.6.8 -> 1.6.10

Semi-automatic update. 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 1.6.10 with grep in /nix/store/xj71q5kp9k5m2nsfydjhjra8axf3kdj8-focuswriter-1.6.10
- found 1.6.10 in filename of file in /nix/store/xj71q5kp9k5m2nsfydjhjra8axf3kdj8-focuswriter-1.6.10