clippy: remove/replace needless explicit lifetimes

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>

src/tools/systemd/time.rs

@@ -142,7 +142,7 @@ impl From<TimeSpan> for f64 {
 }
 
 
-pub fn verify_time_span<'a>(i: &'a str) -> Result<(), Error> {
+pub fn verify_time_span(i: &str) -> Result<(), Error> {
     parse_time_span(i)?;
     Ok(())
 }