Clean up #[transactional] (#11546)

* Deprecate #[transactional] attribute

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Remove #[transactional] from nomination pools

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Review fix

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Fix NOOP test

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Suppress warnings

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/frame/support/procedural/src/lib.rs

@@ -429,6 +429,7 @@ pub fn pallet(attr: TokenStream, item: TokenStream) -> TokenStream {
 /// }
 /// ```
 #[proc_macro_attribute]
+#[deprecated(note = "This is now the default behaviour for all extrinsics.")]
 pub fn transactional(attr: TokenStream, input: TokenStream) -> TokenStream {
 	transactional::transactional(attr, input).unwrap_or_else(|e| e.to_compile_error().into())
 }

substrate/frame/support/src/dispatch.rs

@@ -200,6 +200,7 @@ impl<T> Parameter for T where T: Codec + EncodeLike + Clone + Eq + fmt::Debug +
 ///
 /// Transactional function discards all changes to storage if it returns `Err`, or commits if
 /// `Ok`, via the #\[transactional\] attribute. Note the attribute must be after #\[weight\].
+/// The #\[transactional\] attribute is deprecated since it is the default behaviour.
 ///
 /// ```
 /// # #[macro_use]

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

@@ -15,6 +15,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// Disable warnings for #\[transactional\] being deprecated.
+#![allow(deprecated)]
+
 use frame_support::{
 	assert_noop, assert_ok, assert_storage_noop,
 	dispatch::{DispatchError, DispatchResult},