Migrate validator client to clap derive (#6300)

Partially #5900


  Migrate the validator client cli to clap derive

database_manager/src/cli.rs

@@ -66,16 +66,6 @@ pub struct DatabaseManager {
     )]
     pub backend: store::config::DatabaseBackend,
 
-    #[clap(
-        long,
-        global = true,
-        help = "Prints help information",
-        action = clap::ArgAction::HelpLong,
-        display_order = 0,
-        help_heading = FLAG_HEADER
-    )]
-    help: Option<bool>,
-
     #[clap(subcommand)]
     pub subcommand: DatabaseManagerSubcommand,
 }