Revert "PR: Add libpng and libjpeg-turbo requirement into conda recipe"

[andfoy]

Reverts #2301

[codecov]

Codecov Report

Merging #2375 into master will increase coverage by 2.31%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2375      +/-   ##
==========================================
+ Coverage   68.42%   70.73%   +2.31%     
==========================================
  Files          94       93       -1     
  Lines        7765     7768       +3     
  Branches     1208     1199       -9     
==========================================
+ Hits         5313     5495     +182     
+ Misses       2103     1910     -193     
- Partials      349      363      +14     

Impacted Files	Coverage Δ
torchvision/io/__init__.py	100.00% <ø> (ø)
torchvision/models/detection/transform.py	95.55% <0.00%> (+0.02%)	⬆️
torchvision/ops/poolers.py	97.02% <0.00%> (+0.02%)	⬆️
torchvision/models/inception.py	84.64% <0.00%> (+0.05%)	⬆️
torchvision/models/googlenet.py	82.32% <0.00%> (+0.09%)	⬆️
torchvision/models/detection/roi_heads.py	82.34% <0.00%> (+0.11%)	⬆️
torchvision/models/detection/generalized_rcnn.py	88.33% <0.00%> (+0.19%)	⬆️
torchvision/transforms/transforms.py	77.68% <0.00%> (+0.19%)	⬆️
torchvision/models/detection/_utils.py	67.34% <0.00%> (+0.22%)	⬆️
torchvision/datasets/imagenet.py	82.45% <0.00%> (+0.31%)	⬆️
... and 17 more

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