Add --no-background-compilation to tests that expect to run code in optimized form

tests/language/type_propagation_assert_assignable_test.dart

Index: tests/language/type_propagation_assert_assignable_test.dart
diff --git a/tests/language/type_propagation_assert_assignable_test.dart b/tests/language/type_propagation_assert_assignable_test.dart
index 352a58428855593977a1306550dda8f4747ec316..3a694c391a0d3176303002ce2c17b0889686776f 100644
--- a/tests/language/type_propagation_assert_assignable_test.dart
+++ b/tests/language/type_propagation_assert_assignable_test.dart
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Check that type of the AssertAssignable is recomputed correctly.
-// VMOptions=--optimization-counter-threshold=10 --no-use-osr
+// VMOptions=--optimization-counter-threshold=10 --no-use-osr --no-background-compilation
 
 import "package:expect/expect.dart";