Fix the updated clippy error unused_unit

Now it checks the where clauses as well.
rust-lang/rust-clippy@f20b96277397db2c9021d06c
f8647014ccdc0a39

Author: Junha Yang

core/src/miner/miner.rs

@@ -112,7 +112,7 @@ impl Params {
 
     pub fn apply<F>(&self, f: F)
     where
-        F: FnOnce(&mut AuthoringParams) -> (), {
+        F: FnOnce(&mut AuthoringParams), {
         let mut params = self.params.write();
         f(&mut params);
     }