Removed last z3 mention from docs

[jmafoster1]

Closes #325. I remember removing a bunch of these a while ago, but I found another one. Hopefully this is the last one!

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ PYTHON	black	32		0	0.95s
✅ PYTHON	pylint	32		0	6.02s

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.75%. Comparing base (03d8a7f) to head (8e99112).
Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #335   +/-   ##
=======================================
  Coverage   95.75%   95.75%           
=======================================
  Files          27       27           
  Lines        1624     1624           
=======================================
  Hits         1555     1555           
  Misses         69       69           

---

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[f-allian]

@jmafoster1 Fine for now. The documentation revamp will be a much bigger piece of work in #326