update effective conductivity

[rtimms]

Description

Fixes a bug where the solid phase conductivity was double-corrected for tortuosity when creating parameters from a BPX file. The BPX file already contains the effective conductivity, so no correction needs to be applied (hence we set the Bruggeman coefficient to 0). This same bug was present in the Chen2020 parameter sets.

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist:

• No style issues: $ pre-commit run
• All tests pass: $ python run-tests.py --unit
• The documentation builds: $ cd docs and then $ make clean; make html

You can run all three at once, using $ python run-tests.py --quick.

Further checks:

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works