Fix clippy.

czkawka_core/src/common.rs

@@ -7,6 +7,7 @@ use std::time::SystemTime;
 pub struct Common();
 impl Common {
     /// Printing time which took between start and stop point and prints also function name
+    #[allow(unused_variables)]
     pub fn print_time(start_time: SystemTime, end_time: SystemTime, function_name: String) {
         #[cfg(debug_assertions)]
         println!("Execution of function \"{}\" took {:?}", function_name, end_time.duration_since(start_time).expect("Time cannot go reverse."));