Ignore RUSTSEC-2021-0139

We're currently being dinged by the above RUSTSEC, REF
tokio-rs/tracing#2282. It looks like tracing will
update itself soon but meanwhile `ansi_term` being unmaintained is not a
terrible problem for lading.

Signed-off-by: Brian L. Troutwine <brian.troutwine@datadoghq.com>

deny.toml

@@ -21,6 +21,7 @@ vulnerability = "deny"
 unmaintained = "deny"
 notice = "deny"
 unsound = "deny"
+ignore = [ "RUSTSEC-2021-0139" ]
 
 [bans]
 multiple-versions = "allow"