liquid-water-content: avoid misleading var name

[slayoo]

[slayoo]

CC @yoctoyotta1024

[slayoo]

same here: https://github.com/open-atmos/PySDM/blob/73ccc3d24c62b67bce13565eb181bcef7d1ba3d2/PySDM/products/size_spectral/water_mixing_ratio.py#L34

[codecov[bot]]

Codecov Report

:x: Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 86.50%. Comparing base (d5320fe) to head (ac6f423). :warning: Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...roducts/aqueous_chemistry/aqueous_mole_fraction.py	0.00%	2 Missing :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1730   +/-   ##
=======================================
  Coverage   86.50%   86.50%           
=======================================
  Files         412      412           
  Lines       10372    10372           
=======================================
  Hits         8972     8972           
  Misses       1400     1400           

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[yoctoyotta1024]

CC @yoctoyotta1024

looks good to me! :)