RUSTSEC-2019-0040: `boxfnonce` obsolete with release of Rust 1.35.0

[github-actions[bot]]

boxfnonce obsolete with release of Rust 1.35.0

Details
Status	unmaintained
Package	boxfnonce
Version	0.1.1
URL	https://github.com/stbuehler/rust-boxfnonce/commit/058ac7e1a7d732076da9d8a37baa66bcb67758d8
Date	2019-06-20

This commit marks the boxfnonce crate as obsolete and the GitHub repo has since been archived.

The functionality of boxfnonce has been added to Rust since 1.35.0. Use Box<dyn FnOnce(...) -> ...>.

See advisory page for additional details.