TST: don't skip statsmodels tests on network builds (pandas-dev#18362)

(cherry picked from commit 1798c9d)

Author: jreback

pandas/tests/test_downstream.py

@@ -52,7 +52,6 @@ def test_xarray(df):
     assert df.to_xarray() is not None
 
 
-@tm.network
 def test_statsmodels():
 
     statsmodels = import_module('statsmodels')  # noqa