redis: 4.0.7 -> 4.0.8

Semi-automatic update generated by https://github.com/ryantm/nix-update tools. These checks were done:

- built on NixOS
- ran `/nix/store/jbp7m1gshmk8an8sb14glwijgw1chvvq-redis-4.0.8/bin/redis-server -v` and found version 4.0.8
- ran `/nix/store/jbp7m1gshmk8an8sb14glwijgw1chvvq-redis-4.0.8/bin/redis-server --version` and found version 4.0.8
- ran `/nix/store/jbp7m1gshmk8an8sb14glwijgw1chvvq-redis-4.0.8/bin/redis-benchmark --help` got 0 exit code
- ran `/nix/store/jbp7m1gshmk8an8sb14glwijgw1chvvq-redis-4.0.8/bin/redis-cli -v` and found version 4.0.8
- ran `/nix/store/jbp7m1gshmk8an8sb14glwijgw1chvvq-redis-4.0.8/bin/redis-cli --version` and found version 4.0.8
- found 4.0.8 with grep in /nix/store/jbp7m1gshmk8an8sb14glwijgw1chvvq-redis-4.0.8
- directory tree listing: https://gist.github.com/2870bd85351bae2037f6c3ffd93f9d51