Fixing bug in gradients_generate_sampling

[karanphil]

Quick description

There was a small bug with the argument --no_b0_start, it was missing action='store_true and was just doing nothing.

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Type of change

Check the relevant options.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Provide data, screenshots, command line to test (if relevant)

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Checklist

• My code follows the style guidelines of this project (run autopep8)
• I added relevant citations to scripts, modules and functions docstrings and descriptions
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I moved all functions from the script file (except the argparser and main) to scilpy modules
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[arnaudbore]

Good catch

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.46%. Comparing base (e256482) to head (da8863b).
Report is 59 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1094   +/-   ##
=======================================
  Coverage   69.46%   69.46%           
=======================================
  Files         447      447           
  Lines       24052    24052           
  Branches     3291     3291           
=======================================
  Hits        16708    16708           
  Misses       5946     5946           
  Partials     1398     1398           

Components	Coverage Δ
Scripts	70.26% <100.00%> (ø)
Library	68.39% <ø> (ø)