doclifter: 2.15 -> 2.17

Semi-automatic update. These checks were performed:

- built on NixOS
- ran `/nix/store/l2jl00f6gvvc17lsq27vvmw26md8nf4g-doclifter-2.17/bin/doclifter -V` and found version 2.17
- found 2.17 with grep in /nix/store/l2jl00f6gvvc17lsq27vvmw26md8nf4g-doclifter-2.17
- found 2.17 in filename of file in /nix/store/l2jl00f6gvvc17lsq27vvmw26md8nf4g-doclifter-2.17