moved mdutils to analysis requirements

[meganrm]

Problem

the install failed because it needed mdutils

Solution

mdutils is only used in the analysis code so I moved the requirement there

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.63%. Comparing base (e8c834e) to head (9b808a1).
Report is 16 commits behind head on main.

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Additional details and impacted files

@@           Coverage Diff           @@
##             main     #240   +/-   ##
=======================================
  Coverage   98.63%   98.63%           
=======================================
  Files          18       18           
  Lines         511      511           
=======================================
  Hits          504      504           
  Misses          7        7           

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[github-actions]

Packing analysis report

Analysis for packing results located at cellpack/tests/outputs/test_spheres/spheresSST

Ingredient name	Encapsulating radius	Average number packed
ext_A	25	236.0

Packing image

Distance analysis

Expected minimum distance: 50.00
Actual minimum distance: 50.01

Ingredient key	Pairwise distance distribution
ext_A

[mogres]

Looks like mdutils was the only missing dependency. Hopefully once we re-release to pip we can run an example packing