The only parameter that is ever used is a single directory, make it that only instead of a more complex option structure.
Remove tests.AddFixtures that was the simpler form because it is now redundant.
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Backporting to v11.0 will help with automated backporting of bug fixes in need of custom made fixtures.
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7648
Reviewed-by: Michael Kriese <michael.kriese@gmx.de>
Co-authored-by: Earl Warren <contact@earl-warren.org>
Co-committed-by: Earl Warren <contact@earl-warren.org>
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