Update cargo-deny configuration to fit v2

`cargo-deny` updates its specification in EmbarkStudios/cargo-deny#611
to remove a lot of existing keys that were previously allowed. This was
causing license failures that should have otherwise succeeded.

This updates the underlying configuration to fit the new v2 scheme so
that it will pass.

.deny.toml

@@ -1,8 +1,5 @@
 # https://embarkstudios.github.io/cargo-deny/checks/advisories/cfg.html
 [advisories]
-vulnerability = "deny"
-unmaintained = "deny"
-unsound = "deny"
 yanked = "deny"
 notice = "deny"
 git-fetch-with-cli = true
@@ -15,9 +12,6 @@ wildcards = "allow"
 
 # https://embarkstudios.github.io/cargo-deny/checks/licenses/cfg.html
 [licenses]
-default = "deny"
-unlicensed = "deny"
-copyleft = "deny"
 unused-allowed-license = "deny"
 private.ignore = true
 allow = [