Update tutorial documentation to mention need to delete old files

[jacobcook1995]

Description

This adds to the example run documentation to mention that files from previous runs need to be deleted otherwise errors can crop up. I thought the easiest way to do that was just to tell users to delete the old directory and install a new one (rather than listing specific files that could be problematic). Let me know if you think this is sensible and whether you think that the flow is okay!

Fixes #543

Type of change

• 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)
• Documentation improvement

Key checklist

• Make sure you've run the pre-commit checks: $ pre-commit run -a
• All tests pass: $ poetry run pytest

Further checks

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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.01%. Comparing base (c711fe7) to head (75ace88).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #551   +/-   ##
========================================
  Coverage    95.01%   95.01%           
========================================
  Files           74       74           
  Lines         4235     4235           
========================================
  Hits          4024     4024           
  Misses         211      211           

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[hrlai]

Both the text to remind users to delete previously generated folder and example bash code to do so worked well, thanks!

[davidorme]

@jacobcook1995 That's basically fine. The only thing we could say is that the example is (now) setup to always using the explicit out directory. So we could be a bit cleaner and do the install step once and then get people to delete out (or rename it) if they want to run things again. The advantage of this is it sets people up to do repeated runs from the example data so that they can play around with comparing tweaks to the config etc. etc. rather than just nuking everything and starting from an empty clean copy.