test: ignore filter warnings

Author: qkdreyer

ext/standard/tests/streams/gh15155.phpt

@@ -35,7 +35,7 @@ class DummyWrapper
 
 DummyWrapper::register();
 file_get_contents('dummy://foo', false, \stream_context_create(['dummy' => ['foo' => 'bar']]));
-file_get_contents('php://filter/resource=dummy://foo', false, \stream_context_create(['dummy' => ['foo' => 'bar']]));
+@file_get_contents('php://filter/resource=dummy://foo', false, \stream_context_create(['dummy' => ['foo' => 'bar']]));
 ?>
 --EXPECT--
 string(3) "bar"