fix : remove _{ } syntax from benchmark macro (#7822)

* commented use of common

* hack to pass tests

* another hack

* remove all commented code

* fix the easy tests

* temp hack

* follow through comma hack until better solution

* patch macro

* missed one

* update benchmarks

* update docs

* fix docs

* removed too much

* fix changes

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

substrate/frame/utility/src/benchmarking.rs

@@ -34,8 +34,6 @@ fn assert_last_event<T: Config>(generic_event: <T as Config>::Event) {
 }
 
 benchmarks! {
-	_ { }
-
 	batch {
 		let c in 0 .. 1000;
 		let mut calls: Vec<<T as Config>::Call> = Vec::new();