fix coverage

Author: NimaSarajpoor

stumpy/sdp.py

@@ -306,7 +306,7 @@ def __call__(self, Q, T, n_threads=1, planning_flag="FFTW_ESTIMATE"):
         return real_arr[m - 1 : n]
 
 
-if FFTW_IS_AVAILABLE:
+if FFTW_IS_AVAILABLE:  # pragma: no cover
     _pyfftw_sliding_dot_product = _PYFFTW_SLIDING_DOT_PRODUCT(max_n=2**20)