Subkey should not import the entire world. (#7845)

There is no reason for subkey to import the default Substrate node to
support a feature that would only be usable for the Substrate node.
Subkey itself should be more the default key management binary for
Substrate related chains. If certain chains require some special
functionality, they can easily stick together their own "my-chain-key".

substrate/bin/utils/subkey/src/main.rs

@@ -18,8 +18,6 @@
 
 //! Subkey utility, based on node_runtime.
 
-use node_runtime::Runtime;
-
 fn main() -> Result<(), sc_cli::Error> {
-	subkey::run::<Runtime>()
+	subkey::run()
 }