dtx: Fix typo in command-line interface

Author: qzed

src/cli/dtx.rs

@@ -29,8 +29,8 @@ impl DynCommand for Command {
             .subcommand(SubCommand::with_name("confirm")
                 .about("Confirm latch-open if detachment in progress")
                 .display_order(4))
-            .subcommand(SubCommand::with_name("hearbeat")
-                .about("Send hearbeat if detachment in progress")
+            .subcommand(SubCommand::with_name("heartbeat")
+                .about("Send heartbeat if detachment in progress")
                 .display_order(5))
             .subcommand(SubCommand::with_name("cancel")
                 .about("Cancel any detachment in progress")