Revert test_tsfresh.py: tsfresh works on CPU after numba-cuda removal

Now that numba-cuda is uninstalled on the CPU image, tsfresh/stumpy
imports work without requiring libcudart.so. No need for the skip guard.

Author: stevemessick

tests/test_tsfresh.py

@@ -3,13 +3,8 @@
 import pandas as pd
 import numpy as np
 
-try:
-    from tsfresh import extract_features
-    HAS_TSFRESH = True
-except ImportError:
-    HAS_TSFRESH = False
+from tsfresh import extract_features
 
-@unittest.skipUnless(HAS_TSFRESH, 'tsfresh is not importable (may require CUDA libs)')
 class TestTsFresh(unittest.TestCase):
     def test_extract_feature(self):
         ts = pd.DataFrame({