Fix Chemistry advection fluxes

[henryleberre]

Description

Fixes the chemistry advection fluxes. HLL & HLLC are now correct in >2D.

Type of change

Please delete options that are not relevant.

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

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 45.86%. Comparing base (ca36ffb) to head (cd68c0a).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
src/common/m_variables_conversion.fpp	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #752      +/-   ##
==========================================
- Coverage   45.87%   45.86%   -0.01%     
==========================================
  Files          61       61              
  Lines       16915    16898      -17     
  Branches     1962     1961       -1     
==========================================
- Hits         7759     7751       -8     
+ Misses       7942     7934       -8     
+ Partials     1214     1213       -1     

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[sbryngelson]

@henryleberre can you comment on the status of this PR? ready to go or?