[LLDB] Import decorators in TestPythonOSPlugin.py

This fixes a regression caused by my commit where I added test
as skipped using a decorator but forgot to add import decorator
in TestPythonOSPlugin.py

Author: omjavaid

lldb/test/API/functionalities/plugins/python_os_plugin/TestPythonOSPlugin.py

@@ -5,6 +5,7 @@
 
 import os
 import lldb
+from lldbsuite.test.decorators import *
 from lldbsuite.test.lldbtest import *
 import lldbsuite.test.lldbutil as lldbutil