Make call to scipy.stats.mode compatible with scipy 1.11.0

Starting with scipy 1.11.0, scipy.stats.mode returns a scalar value for
the mode instead of a one-element array. This change was foreshadowed in
scipy version 1.9.0 with the addition of the `keepdims` parameter,
with the eventual goal of setting it to false by default for consistency
with other scipy.stats functions.
See scipy/scipy#16418 for the initial
proposal and scipy/scipy#17561 for the
final change that is now breaking the _demean function.

This commit changes the indexing to be compatible with scipy 1.11.0
and other future versions. I have also tested this change with older
scipy versions up to 0.17.1, which was released in 2016.

Author: HippocampusGirl

sdcflows/workflows/gre.py

@@ -212,7 +212,7 @@ def _demean(in_file, in_mask=None, usemode=True):
 
     if usemode:
         from scipy.stats import mode
-        data[msk] -= mode(data[msk], axis=None)[0][0]
+        data[msk] -= mode(data[msk], axis=None).mode.item()
     else:
         data[msk] -= np.median(data[msk], axis=None)