Fix Kusama coretime config (#221)

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Closes #216

Credits to @bkchr for the suggested fix

Co-authored-by: fellowship-merge-bot[bot] <151052383+fellowship-merge-bot[bot]@users.noreply.github.com>

relay/kusama/src/lib.rs

@@ -1265,7 +1265,7 @@ impl parachains_paras::Config for Runtime {
 	type QueueFootprinter = ParaInclusion;
 	type NextSessionRotation = Babe;
 	type OnNewHead = Registrar;
-	type AssignCoretime = ();
+	type AssignCoretime = CoretimeAssignmentProvider;
 }
 
 parameter_types! {