Fix a typo when checking for Khiops compatibility on the use_complement_as_test feature

[tramora]

Fixes the issue #436

It may be worth adding a UT to test thoroughly the private function _preprocess_task_arguments (as it was first attempted in the discarded PR #230)

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[popescu-v]

I would do a more comprehensive update, according to the comment in the review.

[popescu-v]

2 minor changes: use string interpolation in report names everywhere (see comments).

[popescu-v]

LGTM