Use simpler form for string concatenation

Author: djc

src/cli/self_update.rs

@@ -270,7 +270,7 @@ impl FromStr for SelfUpdateMode {
             _ => Err(anyhow!(format!(
                 "unknown self update mode: '{}'; valid modes are {}",
                 mode,
-                valid_self_update_modes(),
+                Self::modes().join(", "),
             ))),
         }
     }
@@ -1303,14 +1303,6 @@ pub(crate) fn cleanup_self_updater() -> Result<()> {
     Ok(())
 }
 
-pub(crate) fn valid_self_update_modes() -> String {
-    SelfUpdateMode::modes()
-        .iter()
-        .map(|s| format!("'{s}'"))
-        .collect::<Vec<_>>()
-        .join(", ")
-}
-
 #[cfg(test)]
 mod tests {
     use std::collections::HashMap;