Replace latex2sympy's process_sympy with sympy's parse_latex

[willfurnass]

Will hopefully address #300

[codecov-io]

Codecov Report

Merging #348 into master will increase coverage by 0.07%.
The diff coverage is 80.64%.

@@            Coverage Diff             @@
##           master     #348      +/-   ##
==========================================
+ Coverage   68.88%   68.95%   +0.07%     
==========================================
  Files           9        9              
  Lines        5765     5766       +1     
  Branches     1572     1572              
==========================================
+ Hits         3971     3976       +5     
+ Misses       1399     1397       -2     
+ Partials      395      393       -2

Impacted Files	Coverage Δ
mumot/consts.py	100% <100%> (ø)	⬆️
mumot/__init__.py	84.61% <100%> (ø)	⬆️
mumot/utils.py	67.7% <100%> (ø)	⬆️
mumot/views.py	66.2% <71.42%> (ø)	⬆️
mumot/models.py	71.98% <77.77%> (+0.02%)	⬆️
mumot/controllers.py	78.2% <0%> (+0.76%)	⬆️

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[jarmarshall]

I've reviewed the changes, the tests are all passed, this seems good to me. Good to unpin antlr4-python3-runtime (see issue sympy/sympy#17629)... you flagged this as work in progress @willfurnass - any reason not to merge?

[willfurnass]

I've renamed and merged the PR.