[lldb][tests] TestPreferredName.py: Fix for older compilers

This only works as of D145803, where we re-point the
`DW_AT_type` based on existence of `[[clang::preferred_name]]`

(cherry picked from commit b767b05)

Author: Michael137

lldb/test/API/lang/cpp/preferred_name/TestPreferredName.py

@@ -6,8 +6,7 @@
 import lldb
 import lldbsuite.test.lldbutil as lldbutil
 from lldbsuite.test.lldbtest import *
-from lldbsuite.test import decorators
-
+from lldbsuite.test.decorators import *
 
 class TestPreferredName(TestBase):