Corrections in lub tests, cf. flutter#43717, flutter#43720.

The tests least_upper_bound_{futureor,function}_test.dart are corrected:
The expected least upper bound was changed in one case in each test,
because the case matches a rule earlier in the ruleset, so the new rules
are not used in these cases.

Change-Id: I1f5f303ccde10af6084771a90d92d81d636909d6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/166635
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>
Commit-Queue: Erik Ernst <eernst@google.com>

Author: eernstg

tests/language/least_upper_bound/least_upper_bound_function_test.dart

@@ -46,6 +46,6 @@ void main() {
 
   void f7(Function(Function) x, Null y) {
     var z = condition ? x : y;
-    z.expectStaticType<Exactly<Object?>>();
+    z.expectStaticType<Exactly<Function(Function)?>>();
   }
 }

tests/language/least_upper_bound/least_upper_bound_futureor_test.dart

@@ -206,20 +206,16 @@ void main() {
 
   void f20(dynamic a, FutureOr<void> b) {
     var x = condition ? a : b;
-    x.expectStaticType<Exactly<FutureOr<void>>>();
-    if (x is Future) throw 0;
-    /**/ x.toString();
-    //   ^
-    // [analyzer] COMPILE_TIME_ERROR.USE_OF_VOID_RESULT
-    // [cfe] This expression has type 'void' and can't be used.
+    // Verify that the type of `x` is a top type.
+    x.expectStaticType<Exactly<dynamic>>();
+    // Verify that it is `dynamic`.
+    x.unknownMember();
 
     var y = condition ? b : a;
-    y.expectStaticType<Exactly<FutureOr<void>>>();
-    if (y is Future) throw 0;
-    /**/ y.toString();
-    //   ^
-    // [analyzer] COMPILE_TIME_ERROR.USE_OF_VOID_RESULT
-    // [cfe] This expression has type 'void' and can't be used.
+    // Verify that the type of `y` is a top type.
+    y.expectStaticType<Exactly<dynamic>>();
+    // Verify that it is `dynamic`.
+    y.unknownMember();
   }
 
   void f21(A a, B b) {