Remove numpy import from RooDataSet unit test.

The test claims to have no python dependencies, but it was importing
numpy for no reason.

Author: hageboeck

bindings/pyroot/pythonizations/test/roofit/roodataset.py

@@ -2,9 +2,6 @@
 
 import ROOT
 
-import numpy as np
-
-
 class TestRooDataSet(unittest.TestCase):
     def test_createHistogram_decls(self):
         """RooDataSet::createHistogram overloads obtained with using decls."""