Removed sd_a- particle size parameters: mean, standard deviation

[jeromtom]

Description

Problem:
Particle size parameters like mean/standard deviation are defined but not used, potentially leading to a situation where the user changes it but it will have no effect

Considerations:
-There isn't one mean standard deviation parameter in size_distribution_parameter.py but sd_p and sd_n for the area-weighted standard deviation of positive and negative electrodes respectively.
-sd_p and sd_n cannot be directly removed as they are used in the calculations of R_min and R_max which like you said determine the geometry. We can remove to parameter by assigning the default value of 0.3 in the calculations.

Solution:
Removed sd_a parameter (area-weighted particle-size standard deviation) from the codebase.

Fixes #3219

Type of change

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

Key checklist:

• No style issues: $ pre-commit run (see CONTRIBUTING.md for how to set this up to run automatically when committing locally, in just two lines of code)
• All tests pass: $ python run-tests.py --all
• The documentation builds: $ python run-tests.py --doctest

You can run unit and doctests together at once, using $ python run-tests.py --quick.

[jeromtom]

I think the docs build failed because I used a special character in the pull request head to highlight that sd_a is a parameter. The local docs build test had passed.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.01% ⚠️

Comparison is base (f0cc984) 99.71% compared to head (9f472a8) 99.71%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3226      +/-   ##
===========================================
- Coverage    99.71%   99.71%   -0.01%     
===========================================
  Files          248      248              
  Lines        18826    18824       -2     
===========================================
- Hits         18772    18770       -2     
  Misses          54       54              

Files Changed	Coverage Δ
pybamm/parameters/geometric_parameters.py	100.00% <ø> (ø)
pybamm/parameters/lithium_ion_parameters.py	100.00% <ø> (ø)
pybamm/parameters/size_distribution_parameters.py	100.00% <ø> (ø)

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[jeromtom]

The linkChecker has failed because of a timeout from loading/checking one website.

[valentinsulzer]

Looks good, thanks! Can you also remove the mean and standard deviation parameters where they are added to the parameter set in size_distribution_parameters.py?

[valentinsulzer]

Thanks!

[jeromtom]

I think I also have to remove the tests that search for the removed parameter to fix the build checks.
@tinosulzer Kindly confirm

[valentinsulzer]

Yes, you need to replace them with a test for a different parameter that should be added by size_distribution_parameters (e.g. the minimum particle radius)

[jeromtom]

Unsuccessful checks:

1. linkChecker: Timeout with the link https://www.rse.ox.ac.uk/ in README.md
2. benchmarks on PR: Originates from a previously merged PR
3. nox test in Ubuntu 3.10: This PR does not update the requirements of nox or PyBaMM. If the nox tests were recently updated we have to update the hashes also.