chore: nightly clippy fixes

src/tools.rs

@@ -46,7 +46,7 @@ use crate::stock_str;
 
 /// Shortens a string to a specified length and adds "[...]" to the
 /// end of the shortened string.
-pub(crate) fn truncate(buf: &str, approx_chars: usize) -> Cow<str> {
+pub(crate) fn truncate(buf: &str, approx_chars: usize) -> Cow<'_, str> {
     let count = buf.chars().count();
     if count <= approx_chars + DC_ELLIPSIS.len() {
         return Cow::Borrowed(buf);