Migrate away from SimpleDispatchInfo (#5686)

* Migrate away from SimpleDispatchInfo

* Fix imports

* Better doc

* Update lib.rs

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

substrate/frame/support/test/tests/instance.rs

@@ -23,7 +23,7 @@ use frame_support::{
 		DecodeDifferent, StorageMetadata, StorageEntryModifier, StorageEntryType, DefaultByteGetter,
 		StorageEntryMetadata, StorageHasher,
 	},
-	weights::{SimpleDispatchInfo, MINIMUM_WEIGHT},
+	weights::MINIMUM_WEIGHT,
 	StorageValue, StorageMap, StorageDoubleMap,
 };
 use sp_inherents::{ProvideInherent, InherentData, InherentIdentifier, MakeFatalError};
@@ -56,7 +56,7 @@ mod module1 {
 
 			fn deposit_event() = default;
 
-			#[weight = SimpleDispatchInfo::FixedNormal(MINIMUM_WEIGHT)]
+			#[weight = MINIMUM_WEIGHT]
 			fn one(origin) {
 				system::ensure_root(origin)?;
 				Self::deposit_event(RawEvent::AnotherVariant(3));