Main: Remove idle option

This patch removes the idle option introduced in
e3f83ebe8e. It is no
longer needed as the to be added NixOS module now
uses RuntimeDirectoryPreserve=true.

src/main.rs

@@ -1,7 +1,6 @@
 use std::env;
 use std::fs;
 use std::path::PathBuf;
-use std::thread;
 
 use anyhow::Result;
 
@@ -20,18 +19,12 @@ struct Arguments {
 
     /// The path to write the built secret file to
     output_path: PathBuf,
-
-    /// If the process should keep running without doing anything. This is used to keep a systemd service
-    /// running this and the associated RuntimeDirectory alive.
-    #[clap(long, default_value_t = false)]
-    idle: bool,
 }
 
 fn main() -> Result<()> {
     let Arguments {
         contents_path,
         output_path,
-        idle
     } = Arguments::parse();
 
     let mut handlebars = Handlebars::new();
@@ -103,11 +96,5 @@ fn main() -> Result<()> {
 
     sd_notify::notify(true, &[NotifyState::Ready])?;
 
-    if idle {
-        loop {
-            thread::park();
-        }
-    }
-
     Ok(())
 }