cargo: Update dependencies identified by audit

Ran `cargo audit fix` to update the `nix` crate version with available
security fixes.

Note that although `tokio` also has upstream security fixes, the version
is being left since it is specified as a semver major version only. This
means the consumer can choose which minor and patch level version of
`tokio` they use. Ideally of course they would choose the latest version
but this decision should not be enforced by a library crate.

Signed-off-by: James O. D. Hunt <[email protected]>

Cargo.toml

@@ -14,7 +14,7 @@ description = "A Rust version of ttrpc."
 protobuf = { version = "2.0", optional = true }
 bytes = { version = "0.4.11", optional = true }
 libc = { version = "0.2.59", features = [ "extra_traits" ] }
-nix = "0.16.1"
+nix = "0.20.2"
 log = "0.4"
 byteorder = "1.3.2"
 thiserror = "1.0"

example/Cargo.toml

@@ -17,7 +17,7 @@ libc = "0.2.79"
 byteorder = "1.3.2"
 log = "0.4.6"
 simple-logging = "2.0.2"
-nix = "0.16.1"
+nix = "0.20.2"
 ttrpc = { path = "../", features = ["async"] }
 ctrlc = { version = "3.0", features = ["termination"] }
 tokio = { version = "1.0.1", features = ["signal", "time"] }