Make consistent use of 'ncls' instead of 'phi' for ic/bc in TwoPhaseFlow app

[cekees]

Mandatory Checklist

Please ensure that the following criteria are met:

• [x] Title of pull request describes the changes/features
• [x] Request at least 2 reviewers
• [x] If new files are being added, the files are no larger than 100kB. Post the file sizes.
• [x] Code coverage did not decrease. If this is a bug fix, a test should cover that bug fix. If a new feature is added, a test should be made to cover that feature.
• [x] New features have appropriate documentation strings (readable by sphinx)
• [x] Contributor has read and agreed with CONTRIBUTING.md and has added themselves to CONTRIBUTORS.md

As a general rule of thumb, try to follow PEP8 guidelines.

Description

[codecov[bot]]

Codecov Report

Merging #1158 into master will decrease coverage by 0.00%. The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1158      +/-   ##
==========================================
- Coverage   51.76%   51.76%   -0.01%     
==========================================
  Files         540      540              
  Lines      103400   103400              
==========================================
- Hits        53530    53529       -1     
- Misses      49870    49871       +1     

Impacted Files	Coverage Δ
proteus/TwoPhaseFlow/utils/Parameters.py	79.26% <0.00%> (ø)
proteus/tests/test_boundaryconditions.py	97.33% <0.00%> (-0.13%)	:arrow_down:

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[jhcollins]

I feel like I've fixed this in a pr like 3 other times. weird