petsc: 3.8.3 -> 3.8.4

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

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

These checks were done:

- built on NixOS
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/saws/getSAWs.bash -h` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/saws/getSAWs.bash --help` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/saws/getSAWs.bash help` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/petscdiff -h` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/petscdiff --help` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/petscdiff -h` and found version 3.8.4
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/petscdiff --help` and found version 3.8.4
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/update.py -h` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/update.py --help` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/update.py help` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/update.py -V` and found version 3.8.4
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/update.py -v` and found version 3.8.4
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/update.py --version` and found version 3.8.4
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/update.py version` and found version 3.8.4
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/update.py -h` and found version 3.8.4
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/update.py --help` and found version 3.8.4
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/update.py help` and found version 3.8.4
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/sendToJenkins -h` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/sendToJenkins --help` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/petscnagupgrade.py -h` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/petscnagupgrade.py --help` got 0 exit code
- ran `/nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4/bin/petscnagupgrade.py help` got 0 exit code
- found 3.8.4 with grep in /nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4
- found 3.8.4 in filename of file in /nix/store/czmq31v2xa85ql17whbn05774cncbr4a-petsc-3.8.4
- directory tree listing: https://gist.github.com/da90b8c44c7ed274deb2e1a2c7de8dad