pallet-collator-selection: correctly register weight in new_session (…

…paritytech#5430)

The `pallet-collator-selection` is not correctly using the weight for
the
[new_session](https://github.com/blockdeep/pallet-collator-staking/blob/main/src/benchmarking.rs#L350-L353)
function.

The first parameter is the removed candidates, and the second one the
original number of candidates before the removal, but both values are
swapped.

cumulus/pallets/collator-selection/src/lib.rs

@@ -972,7 +972,7 @@ pub mod pallet {
 			let result = Self::assemble_collators();
 
 			frame_system::Pallet::<T>::register_extra_weight_unchecked(
-				T::WeightInfo::new_session(candidates_len_before, removed),
+				T::WeightInfo::new_session(removed, candidates_len_before),
 				DispatchClass::Mandatory,
 			);
 			Some(result)

prdoc/pr_5430.prdoc

@@ -0,0 +1,13 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: "pallet-collator-selection: correctly register weight in `new_session`"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      - Fixes an incorrect usage of the `WeightInfo` trait for `new_session`.
+
+crates:
+  - name: pallet-collator-selection
+    bump: patch