[gardening] Fix stress test list.

Follow-up to 752a913 which deleted some tests.

Change-Id: Ic75ac76fddf41b790381a9be1c8a90aa6ec10e9e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/400149
Commit-Queue: Alexander Aprelev <[email protected]>
Reviewed-by: Liam Appelbe <[email protected]>

Author: aam

runtime/tests/concurrency/stress_test_list.json

@@ -607,14 +607,9 @@
   "../../../tests/language/accessor_conflict/import_prefixed2_test.dart",
   "../../../tests/language/accessor_conflict/import_prefixed_test.dart",
   "../../../tests/language/accessor_conflict/import_test.dart",
-  "../../../tests/language/argument/assignability_function_typed_runtime_4_test.dart",
-  "../../../tests/language/argument/assignability_function_typed_runtime_5_test.dart",
-  "../../../tests/language/argument/assignability_function_typed_runtime_6_test.dart",
-  "../../../tests/language/argument/assignability_function_typed_runtime_7_test.dart",
   "../../../tests/language/argument/assignability_function_typed_runtime_test.dart",
   "../../../tests/language/argument/named_argument_test.dart",
   "../../../tests/language/argument/named_in_const_creation_test.dart",
-  "../../../tests/language/argument/not_enough_positional_runtime_test.dart",
   "../../../tests/language/assert/assignable_type_test.dart",
   "../../../tests/language/assert/initializer_const_error2_runtime_test.dart",
   "../../../tests/language/assert/initializer_const_error_runtime_test.dart",