deprecated net2 in outdated mio dependency

[extrawurst]

the mio dependency needs to be upgraded to 0.7 to remove net2 from the dependency tree: tokio-rs/mio#1322

right now cargo audit returns:

Crate:  net2
Title:  `net2` crate has been deprecated; use `socket2` instead
Date:   2020-05-01
URL:    https://rustsec.org/advisories/RUSTSEC-2020-0016
Dependency tree:
net2 0.2.34
├── miow 0.2.1
│   └── mio 0.6.22
│       ├── tokio 0.2.21
│       │   └── crossterm 0.17.3
│       ├── signal-hook 0.1.15
│       │   └── crossterm 0.17.3
│       ├── mio-uds 0.6.8
│       │   ├── tokio 0.2.21
│       │   └── async-std 1.5.0
│       │       └── crossterm 0.17.3
│       ├── mio-named-pipes 0.1.6
│       │   └── tokio 0.2.21
│       ├── crossterm 0.17.3
│       └── async-std 1.5.0
└── mio 0.6.22

[extrawurst]

confirmed fixed in 0.17.6