Update scribo-tests with correct k parameters for sauvola-ms-fg

[kba]

@bertsky in OCR-D/ocrd_olena#42 (comment)

The CI failure speaks of the need to update our reference data as well: data/scribo-test/data/OCR-D-IMG-BIN-SAUVOLA-MS-FG/OCR-D-SEG-PAGE-SAUVOLA-MS-FG-orig_tiff-BIN_sauvola-ms-fg.png should now be generated with --all-k 0.34 in effect (instead of the previous result which silently used --k2 0.2 --k3 0.3 --k4 0.5).

(I know: this does decrease the quality for this algorithm even further. But this is not a good time to discuss a good way to wrap the different parameterizations. If we want to have control over k for all impl, we must accept that the k2/k3/k4 difference will disappear.)

[kba]

Fixed in #72