cli: Fix argument value names in auth and init

We decided to use the value names to indicate which type the value
is parsed into (instead of just saying that the value is a `STRING`).

This makes the value names consistent with other commands again.

crates/radicle-cli/src/commands/auth/args.rs

@@ -12,7 +12,7 @@ methods disables the passphrase prompt.
 #[command(about = ABOUT, long_about = LONG_ABOUT, disable_version_flag = true)]
 pub struct Args {
     /// When initializing an identity, sets the node alias
-    #[arg(long, value_name = "STRING")]
+    #[arg(long)]
     pub alias: Option<Alias>,
 
     /// Read passphrase from stdin