clean up new C++ warning tests

tests/errors/w_numpy_arr_as_cppvec_ref.pyx

 # mode: error
-# tag: werror
+# tag: cpp, werror
 
 import numpy as np
 cimport numpy as np
@@ -28,28 +28,4 @@ _ERRORS = """
 18:28: Cannot pass Python object as C++ data structure reference (vector[int] &), will pass by copy.
 19:31: Cannot pass Python object as C++ data structure reference (vector[int] &), will pass by copy.
 19:36: Cannot pass Python object as C++ data structure reference (vector[int] &), will pass by copy.
-31:15: '<init>' redeclared
-31:15: '<init>' redeclared
-32:15: '<init>' redeclared
-32:15: '<init>' redeclared
-32:15: '<init>' redeclared
-33:15: '<init>' redeclared
-33:15: '<init>' redeclared
-33:15: '<init>' redeclared
-34:15: '<init>' redeclared
-44:19: 'assign' redeclared
-44:19: 'assign' redeclared
-45:35: 'assign' redeclared
-55:22: 'erase' redeclared
-55:22: 'erase' redeclared
-56:22: 'erase' redeclared
-58:23: 'insert' redeclared
-58:23: 'insert' redeclared
-59:19: 'insert' redeclared
-59:19: 'insert' redeclared
-59:19: 'insert' redeclared
-60:19: 'insert' redeclared
-69:19: 'resize' redeclared
-69:19: 'resize' redeclared
-70:19: 'resize' redeclared
 """

tests/errors/w_python_list_as_cppset_ref.pyx

 # mode: error
-# tag: werror
+# tag: cpp, werror
 
 from libcpp.set cimport set
 
@@ -15,27 +15,5 @@ def pass_py_obj_as_cpp_cont_ref():
 
 
 _ERRORS = """
-5:13: '<init>' redeclared
-5:13: '<init>' redeclared
-6:13: '<init>' redeclared
-6:13: '<init>' redeclared
-6:13: '<init>' redeclared
-6:13: '<init>' redeclared
-6:13: '<init>' redeclared
-7:13: '<init>' redeclared
-7:13: '<init>' redeclared
-7:13: '<init>' redeclared
 14:33: Cannot pass Python object as C++ data structure reference (set[int] &), will pass by copy.
-21:12: '<init>' redeclared
-21:12: '<init>' redeclared
-22:12: '<init>' redeclared
-40:18: 'erase' redeclared
-40:18: 'erase' redeclared
-41:18: 'erase' redeclared
-41:18: 'erase' redeclared
-41:18: 'erase' redeclared
-42:20: 'erase' redeclared
-45:35: 'insert' redeclared
-45:35: 'insert' redeclared
-46:23: 'insert' redeclared
 """