Mark service/call_site_data_test as flaky on linux

runtime/observatory/tests/service/service.status

Index: runtime/observatory/tests/service/service.status
diff --git a/runtime/observatory/tests/service/service.status b/runtime/observatory/tests/service/service.status
index 687f02d819fa86396883e45956c9c1b29dc9d5da..d3c936e9a2a93a58e06cbadded2f8d42a86230d3 100644
--- a/runtime/observatory/tests/service/service.status
+++ b/runtime/observatory/tests/service/service.status
@@ -2,6 +2,9 @@
 # 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.
 
+[ $system == linux ]
+call_site_data_test: Pass, Fail # Issue 23160
+
 # Unexpected number format
 [ $system == windows ]
 code_test: Skip
@@ -21,4 +24,4 @@ debugging_test: Skip
 
 # All tests use dart:io
 [ $browser || $compiler == dart2js ]
-*: SkipByDesign
+*: SkipByDesign