Remove unneded conversion

src/verify.rs

@@ -192,8 +192,7 @@ impl Unvalidated {
         if let Some(date) = self.date {
             if let Ok(datetime) = date.parse::<HttpDate>() {
                 let system_time = SystemTime::from(datetime);
-                let datetime: SystemTime = system_time.into();
-                if datetime + expires_after < self.parsed_at {
+                if system_time + expires_after < self.parsed_at {
                     return Err(ValidateError::Expired);
                 }
             }