Do not stop CI by cargo-deny multiple-versions error

Author: taiki-e

.deny.toml

@@ -10,9 +10,8 @@ ignore = []
 
 # https://embarkstudios.github.io/cargo-deny/checks/bans/cfg.html
 [bans]
-multiple-versions = "deny"
+multiple-versions = "warn"
 wildcards = "allow" # https://github.com/EmbarkStudios/cargo-deny/issues/448
-skip = []
 
 # https://embarkstudios.github.io/cargo-deny/checks/licenses/cfg.html
 [licenses]