Remove unused Output saving mechanism

[ethanwharris]

What does this PR do?

Fixes #947

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[codecov]

Codecov Report

Merging #948 (e46b09b) into master (4a8615f) will increase coverage by 0.08%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master     #948      +/-   ##
==========================================
+ Coverage   88.32%   88.41%   +0.08%     
==========================================
  Files         243      243              
  Lines       13059    13025      -34     
==========================================
- Hits        11535    11516      -19     
+ Misses       1524     1509      -15     

Flag	Coverage Δ
unittests	88.41% <50.00%> (+0.08%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
flash/core/data/data_pipeline.py	96.85% <ø> (+1.16%)	⬆️
flash/core/data/utils.py	95.16% <ø> (ø)
flash/core/data/io/output_transform.py	97.77% <50.00%> (+14.44%)	⬆️

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