resolve ambiguous dtype in Downsample

[garrettwrong]

It's a brave new world out there.

(Pdb) out.real.dtype
dtype('float32')
(Pdb) out.real.get().dtype
dtype('float32')
(Pdb) (out.real * ds_res**2 / self.resolution**2).dtype
dtype('float64')
(Pdb) type(out)
<class 'cupy.ndarray'>
(Pdb) (out.real.get() * ds_res**2 / self.resolution**2).dtype
dtype('float32')

There are other ways to handle, but this seemed minimally invasive. Resolves the problem I was seeing in the pipeline demo.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.60%. Comparing base (52d3ce6) to head (13544c9).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1298   +/-   ##
========================================
  Coverage    90.60%   90.60%           
========================================
  Files          133      133           
  Lines        14346    14346           
========================================
  Hits         12998    12998           
  Misses        1348     1348           

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[j-c-c]

Fun stuff!

[garrettwrong]

Merging.