fix date topython

[tlambert03]

fixes bug in converting QDate objects to python in PyQt5

[codecov]

Codecov Report

Merging #123 (06c209d) into master (b81fbf4) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master     #123   +/-   ##
=======================================
  Coverage   90.33%   90.33%           
=======================================
  Files          25       25           
  Lines        2443     2443           
=======================================
  Hits         2207     2207           
  Misses        236      236           

Impacted Files	Coverage Δ
magicgui/backends/_qtpy/widgets.py	84.93% <0.00%> (ø)

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