Remove deepcopy

[surdouski]

Just found this one after updating something internal and hitting serialization issue again. See previous PR regarding deepcopy (they have no purpose).

[MSeal]

There is a purpose to deepcopy, in the interface, but I agree removing it should be expected at this point. Very early on there was more manipulation of nbformat objects and some implicit expectations that the input wouldn't be modified. Mostly when scrapbook code was still part of papermill. Not as much of a concern now-a-days so happy to merge it.

[surdouski]

I figured I could quickly update this in browser, I'll wait till I'm home later today to actually pull everything down and run the tests locally before committing anything else to the branch.

[codecov]

Codecov Report

Merging #694 (812e46c) into main (fdf4880) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #694      +/-   ##
==========================================
- Coverage   91.86%   91.86%   -0.01%     
==========================================
  Files          17       17              
  Lines        1623     1622       -1     
==========================================
- Hits         1491     1490       -1     
  Misses        132      132              

Impacted Files	Coverage Δ
papermill/engines.py	98.36% <100.00%> (-0.01%)	⬇️

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[surdouski]

@MSeal Can this be merged? Thanks.