[cfe/ffi] Remove custom FFI checks covered by class modifiers

Tests are in the following files 3.0 and pre-3.0 respectively.
TEST=tests/ffi/vmspecific_static_checks_test.dart
TEST=tests/ffi_2/vmspecific_static_checks_test.dart

Bug: https://github.com/dart-lang/sdk/issues/51683
Change-Id: Ib0b27590748ef788c5475929fde585c790f64e63
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/291064
Reviewed-by: Martin Kustermann <kustermann@google.com>
Reviewed-by: Kallen Tu <kallentu@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>
diff --git a/pkg/front_end/testcases/class_modifiers/ffi_exception.dart.strong.transformed.expect b/pkg/front_end/testcases/class_modifiers/ffi_exception.dart.strong.transformed.expect
index b1d004c..e204089 100644
--- a/pkg/front_end/testcases/class_modifiers/ffi_exception.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/class_modifiers/ffi_exception.dart.strong.transformed.expect
@@ -1,8 +1,6 @@
 //
 // Problems outside component:
 //
-// pkg/front_end/testcases/class_modifiers/ffi_exception.dart: Error: Class 'NativeType' cannot be extended or implemented.
-//
 // pkg/front_end/testcases/class_modifiers/ffi_exception.dart: Error: Class 'Object' cannot be extended or implemented.
 //
 library /*isNonNullableByDefault*/;
diff --git a/pkg/front_end/testcases/class_modifiers/ffi_exception.dart.weak.transformed.expect b/pkg/front_end/testcases/class_modifiers/ffi_exception.dart.weak.transformed.expect
index b1d004c..e204089 100644
--- a/pkg/front_end/testcases/class_modifiers/ffi_exception.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/class_modifiers/ffi_exception.dart.weak.transformed.expect
@@ -1,8 +1,6 @@
 //
 // Problems outside component:
 //
-// pkg/front_end/testcases/class_modifiers/ffi_exception.dart: Error: Class 'NativeType' cannot be extended or implemented.
-//
 // pkg/front_end/testcases/class_modifiers/ffi_exception.dart: Error: Class 'Object' cannot be extended or implemented.
 //
 library /*isNonNullableByDefault*/;
diff --git a/pkg/vm/lib/transformations/ffi/use_sites.dart b/pkg/vm/lib/transformations/ffi/use_sites.dart
index ea3cbe6..1e96ef7 100644
--- a/pkg/vm/lib/transformations/ffi/use_sites.dart
+++ b/pkg/vm/lib/transformations/ffi/use_sites.dart
@@ -785,12 +785,6 @@
       }
     }
 
-    for (final parent in nativeTypesClasses.values) {
-      if (hierarchy.isSubtypeOf(klass, parent)) {
-        return parent;
-      }
-    }
-
     return null;
   }