memcached: 1.5.7 -> 1.5.8 (#41110)

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

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

These checks were done:

- built on NixOS
- /nix/store/jfhla2f3268dkbi1frd8g1d46cj6f1xm-memcached-1.5.8/bin/memcached passed the binary check.
- 1 of 1 passed binary check by having a zero exit code.
- 1 of 1 passed binary check by having the new version present in output.
- found 1.5.8 with grep in /nix/store/jfhla2f3268dkbi1frd8g1d46cj6f1xm-memcached-1.5.8
- directory tree listing: https://gist.github.com/69a417ed0d192d2c714645a464ec2ba5
- du listing: https://gist.github.com/94f5ac6323482d6fb77b7fe42d8814a9