[lldb] Remove an unused using decl (NFC)

Author: kazutakahirata

lldb/unittests/ScriptInterpreter/Python/PythonDataObjectsTests.cpp

@@ -23,7 +23,6 @@
 
 using namespace lldb_private;
 using namespace lldb_private::python;
-using llvm::Error;
 using llvm::Expected;
 
 class PythonDataObjectsTest : public PythonTestSuite {