Feat: Use distance twice in template for step distribution case

[AurelienJaquier]

use distance twice in jinja template for step distribution case

Description

Step distributions need to have distance twice in the hoc file in order to be usable.
This does not affect other distributions, they will still be working as before.
This was already implemented in BluePyOpt and BluePyEModel (see e.g. https://github.com/BlueBrain/BluePyOpt/blob/master/bluepyopt/ephys/templates/cell_template.jinja2#L127)

Checklist

This pull request is:

• A documentation / typographical error fix
  • Good to go, no issue or tests are needed
• A short code fix
  • Please include: Fixes: #<issue number> in the description if it solves an existing issue
    (which must include a complete example of the issue).
  • Please include tests that fail with the main branch and pass with the provided fix.
• A new feature implementation or update an existing feature
  • Please include: Fixes: #<issue number> in the description if it solves an existing issue
    (which must include a complete example of the feature).
  • Please include tests that cover every lines of the new/updated feature.
  • Please update the documentation to describe the new/updated feature.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 37.15%. Comparing base (cc2e462) to head (b3d983c).
Report is 31 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #66      +/-   ##
==========================================
- Coverage   37.87%   37.15%   -0.72%     
==========================================
  Files          23       19       -4     
  Lines        6245     5929     -316     
  Branches     1215     1090     -125     
==========================================
- Hits         2365     2203     -162     
+ Misses       3599     3473     -126     
+ Partials      281      253      -28     

Flag	Coverage Δ
pytest	37.15% <ø> (-0.72%)	⬇️

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see 18 files with indirect coverage changes