Remove `fetch_recipe.py`

[ehogan]

The fetch_recipe.py module was added to CMEW via #477. This module directly uses an environment variable from Cylc. This environment variable caused problems when creating the cmewpy package (#511).

The fetch_recipe.py module should either be:

• removed, and replaced with code added directly to CMEW
  • this would reduce the amount of code in the repository and simplify CMEW
• updated, such that the code does not use any environment variables Done via Remove environment variables from fetch_recipe.py #533
  • ideally, we would do this anyway for all Python modules Done via Remove all environment variables from Python modules #517

[ehogan]

The changes in #557 uses esmvaltool recipes list | grep $CYLC_TASK_PARAM_recipe.

I am confident this will work every time due to the outputs of these commands:

% esmvaltool recipes list | gawk -F "/" "{print $NF}" | wc -l
221
% esmvaltool recipes list | gawk -F "/" "{print $NF}" | uniq -d | wc -l
0

where:

• -F = the field separator (some recipes are located in directories)
• $NF = the last entry on the line (the recipe name)
• uniq -d = return only duplicated lines