api!: remove key_gen_type config

This removes the ability to generate RSA keys.

src/config.rs

@@ -193,10 +193,6 @@ pub enum Config {
     #[strum(props(default = "1"))]
     FetchedExistingMsgs,
 
-    /// Type of the OpenPGP key to generate.
-    #[strum(props(default = "0"))]
-    KeyGenType,
-
     /// Timer in seconds after which the message is deleted from the
     /// server.
     ///