Document helper script instructions are incorrect

[jonathan-greig]

The instructions in docs/recipe-list.md generated by docs/generate_recipe_doc.py say to generate the recipe list by running:

poetry install -d
python docs/generate_recipe_doc.py data/recipes

But neither of these commands work:

$ poetry install -d

The option "-d" does not exist

$ python docs/generate_recipe_doc.py data/recipes
Traceback (most recent call last):
  File "/usr/local/google/home/jonathangreig/projects/dftimewolf/dftimewolf/docs/generate_recipe_doc.py", line 163, in <module>
    outputdir = os.path.abspath(sys.argv[2])
IndexError: list index out of range