remove shoulder peaks: use fork instead of spawn for multiprocessing test

tests/test_remove_shoulder_peaks.py

@@ -40,7 +40,6 @@ def test_remove_shoulder_peaks_parallel(data_path, tmpdir):
 
     pm = PeakMap.load(data_path("test_smallest.mzXML"))
 
-    # multiprocessing.set_start_method("spawn")
     with multiprocessing.Pool(2) as p:
         args = dill.dumps((remove_shoulder_peaks, pm, parameters))
         results = p.map(execute, [args, args])