misc/keygen: set publish to false in Cargo.toml since this is a priva…

…te package (libp2p#2635)

misc/keygen/Cargo.toml

@@ -7,6 +7,7 @@ license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
 keywords = ["peer-to-peer", "libp2p", "networking"]
 categories = ["network-programming", "asynchronous"]
+publish = false
 
 [dependencies]
 clap = {version = "3.1.6", features = ["derive"]}