Simplify deposit_event declaration in decl_module (#3506)

* simplify module deposit_event declaration

* fix

* bump version

* fix

* fix test

* fix doc

substrate/srml/contracts/src/lib.rs

@@ -504,7 +504,7 @@ decl_module! {
 		/// default value is 10_000_000.
 		const BlockGasLimit: Gas = T::BlockGasLimit::get();
 
-		fn deposit_event<T>() = default;
+		fn deposit_event() = default;
 
 		/// Updates the schedule for metering contracts.
 		///