fix: use version = 2 in deny.toml

New versions of `cargo deny` default all warnings to deny by default,
and removed the possibility to configure them (e.g. the `unlicensed` and
`copyleft` options are removed, with the default behavior now being as
if they had been set to `deny` before).

We opt-in to this new behavior by setting `version = 2` and removing the
now unsupported configuration options, to avoid a warning from being
printed (which would cause our `test_licences` test to fail).

Signed-off-by: Patrick Roy <[email protected]>

deny.toml

@@ -1,4 +1,5 @@
 [licenses]
+version = 2
 allow = [
     "MIT",
     "Apache-2.0",
@@ -8,12 +9,6 @@ allow = [
     "OpenSSL"
 ]
 
-# Lint level for licenses considered copyleft
-copyleft = "deny"
-
-# The lint level for crates which do not have a detectable license
-unlicensed = "deny"
-
 [[bans.deny]]
 name = "serde_derive"
 version = ">1.0.171, < 1.0.184"