Fix naming conventions to match C++ library

[apulsipher]

Make epiworldR version of LFMCMC consistent with changes in C++ library.

This shouldn't be merged until UofUEpiBio/epiworld#37 is merged.

[codecov]

Codecov Report

Attention: Patch coverage is 96.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 36.15%. Comparing base (174263f) to head (50346c8).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
R/LFMCMC.R	88.88%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #58   +/-   ##
=======================================
  Coverage   36.15%   36.15%           
=======================================
  Files          36       36           
  Lines        1975     1975           
=======================================
  Hits          714      714           
  Misses       1261     1261           

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[gvegayon]

Thank you, @apulsipher. Once the couple of comments are addressed, feel free to merge.

[apulsipher]

Thank you, @apulsipher. Once the couple of comments are addressed, feel free to merge.

@gvegayon Thanks for looking at this! Have you also looked at the C++ library PR? I feel we should merge that one first