Fixing Mutation of 2d tensors in to_pil_image

[surgan12]

closes #760

[codecov-io]

Codecov Report

Merging #762 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #762   +/-   ##
=======================================
  Coverage   40.31%   40.31%           
=======================================
  Files          29       29           
  Lines        2746     2746           
  Branches      432      432           
=======================================
  Hits         1107     1107           
  Misses       1563     1563           
  Partials       76       76

Impacted Files	Coverage Δ
torchvision/transforms/functional.py	70.47% <100%> (ø)	⬆️

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[fmassa]

Thanks!