build: allow Zlib license in cargo-deny configuration

Add Zlib to the list of accepted licenses to support new dependencies or updates that utilize this license.

deny.toml

@@ -44,6 +44,7 @@ allow = [
     "Apache-2.0",
     "Unicode-3.0",
     "BSD-3-Clause",
+    "Zlib"
 ]
 
 exceptions = [