Fix attribute conflict from non-removed "regions" in BoutDataArray.ddy()

[johnomotani]

No description provided.

[codecov-commenter]

Codecov Report

Merging #222 (7e6c092) into master (943d4fb) will decrease coverage by 0.06%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master     #222      +/-   ##
==========================================
- Coverage   75.41%   75.34%   -0.07%     
==========================================
  Files          14       14              
  Lines        2652     2645       -7     
  Branches      625      626       +1     
==========================================
- Hits         2000     1993       -7     
+ Misses        421      420       -1     
- Partials      231      232       +1     

Impacted Files	Coverage Δ
xbout/boutdataarray.py	77.87% <50.00%> (+0.73%)	⬆️
xbout/plotting/animate.py	45.21% <0.00%> (-0.87%)	⬇️
xbout/utils.py	82.73% <0.00%> (-0.30%)	⬇️
xbout/boutdataset.py	75.36% <0.00%> (-0.25%)	⬇️
xbout/calc/tests/test_turbulence.py	100.00% <0.00%> (ø)

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