chore: remove singularity tools and update haiku version

[limbryan]

Related issues: #146

This PR :

• removes singularity tools and related documentation to remove the need to maintain a redundancy. singularity can still be used but can just be installed with pip (via pypi) or with the requirements.txt file directly.
• updates haiku version to stop jax warnings for tree_utils.

Checks

• [x] a clear description of the PR has been added
• [x] sufficient tests have been written (N/A)
• [x] relevant section added to the documentation
• [x] example notebook added to the repo (N/A)
• [x] clean docstrings and comments have been written (N/A)
• [x] if any issue/observation has been discovered, a new issue has been opened

[codecov-commenter]

Codecov Report

Merging #147 (12124eb) into develop (6fa19e7) will increase coverage by 0.01%. The diff coverage is n/a.

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@@             Coverage Diff             @@
##           develop     #147      +/-   ##
===========================================
+ Coverage    92.28%   92.29%   +0.01%     
===========================================
  Files          116      116              
  Lines         6763     6772       +9     
===========================================
+ Hits          6241     6250       +9     
  Misses         522      522              

see 14 files with indirect coverage changes

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