bug: some tests are broken due to fixing dependency cycles

[iqdecay]

This example cannot run for instance, because of the fact that we can't import setup_test_provider.
Three alternatives (n°1 is my fav):

• Remove this example (and the ones like it) altogether, and count on the MDBOOK to do its work
• Re-introduce the fuels-helpers dependency but re-create a dependency cycle just for having a working example
• Add the ignore tag to this example, but then it's not tested and easily gets out of sync with the code

[iqdecay]

This was inadvertently fixed using n°1 in #848. Can be reopened if necessary.