Update nix requirement from 0.19.0 to 0.23.1

[dependabot[bot]]

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Updates the requirements on nix to permit the latest version.

Changelog

Sourced from nix's changelog.

[0.23.1] - 2021-12-16

Added

Changed

• Relaxed the bitflags requirement from 1.3.1 to 1.1. This partially reverts #1492. From now on, the MSRV is not guaranteed to work with all versions of all dependencies, just with some version of all dependencies. (#1607)

Fixed

• Fixed soundness issues in FdSet::insert, FdSet::remove, and FdSet::contains involving file descriptors outside of the range 0..FD_SETSIZE. (#1575)

Removed

[0.23.0] - 2021-09-28

Added

• Added the LocalPeerCred sockopt. (#1482)
• Added TimeSpec::from_duration and TimeSpec::from_timespec (#1465)
• Added IPV6_V6ONLY sockopt. (#1470)
• Added impl From<User> for libc::passwd trait implementation to convert a User into a libc::passwd. Consumes the User struct to give ownership over the member pointers. (#1471)
• Added pthread_kill. (#1472)
• Added mknodat. (#1473)
• Added setrlimit and getrlimit. (#1302)
• Added ptrace::interrupt method for platforms that support PTRACE_INTERRUPT (#1422)
• Added IP6T_SO_ORIGINAL_DST sockopt. (#1490)
• Added the PTRACE_EVENT_STOP variant to the sys::ptrace::Event enum (#1335)
• Exposed SockAddr::from_raw_sockaddr (#1447)
• Added TcpRepair (#1503)
• Enabled pwritev and preadv for more operating systems. (#1511)

... (truncated)

Commits

• afba7c5 (cargo-release) version 0.23.1
• 81c0cf4 Merge #1608
• 79ee0a5 Merge #1607
• 178ea09 Relax the bitflags dependency from 1.3.1 to 1.1
• cde860c [skip ci] Update cargo-release syntax in the docs
• 5197647 Merge #1561
• a037c33 Merge #1606
• ac159d9 Pin the nightly compiler version used with DragonflyBSD
• 77bc02e Update the OSX test environment for Big Sur
• 3c52c56 Test preadv and pwritev on more operating systems
• Additional commits viewable in compare view

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