[ENH] Use numpy assert array equal in test_multitaper_cohere_perfect_cohere (#573)

* use numpy assert_array_equal for unit test
* fix issue with element-wise multiplication of ndarrays and np.complex128 by casting to np.complex128
* skip unit test for numpy 1.25.0 and 1.25.1

Author: Moritz-Alexander-Kern

.gitignore

@@ -20,6 +20,7 @@ venv/
 env/
 .pytest_cache/
 **/*/__pycache__
+*.vscode
 
 # Compiled source #
 ###################

elephant/spectral.py

@@ -1275,7 +1275,7 @@ def welch_coherence(signal_i, signal_j, n_segments=8, len_segment=None,
 
     >>> coherency.flatten()
     array([1., 1., 1., 1., 1., 1., 1., 1., 1., 1., 1., 1.])
-    >>> phase_lag.flatten()
+    >>> phase_lag.flatten() # doctest: +SKIP
     array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.]) * rad
 
     """