Update mangling test for optional-printing change

Author: DougGregor

test/Demangle/Inputs/manglings.txt

@@ -407,5 +407,5 @@ $sScA ---> Swift.Actor
 $sScGySiG ---> Swift.TaskGroup<Swift.Int>
 $s4test10returnsOptyxycSgxyScMYccSglF ---> test.returnsOpt<A>((@Swift.MainActor () -> A)?) -> (() -> A)?
 $sSvSgA3ASbIetCyyd_SgSbIetCyyyd_SgD ---> (@escaping @convention(thin) @convention(c) (@unowned Swift.UnsafeMutableRawPointer?, @unowned Swift.UnsafeMutableRawPointer?, @unowned (@escaping @convention(thin) @convention(c) (@unowned Swift.UnsafeMutableRawPointer?, @unowned Swift.UnsafeMutableRawPointer?) -> (@unowned Swift.Bool))?) -> (@unowned Swift.Bool))?
-$s4test10returnsOptyxycSgxyScMYccSglF ---> test.returnsOpt<A>(@Swift.MainActor () -> A?) -> () -> A?
+$s4test10returnsOptyxycSgxyScMYccSglF ---> test.returnsOpt<A>((@Swift.MainActor () -> A)?) -> (() -> A)?
 $s1t10globalFuncyyAA7MyActorCYiF ---> t.globalFunc(isolated t.MyActor) -> ()