Remove redundent if-statement
Remove redundent if-statement

The if-statement as written was not applying any changes.

`concentric_skinfill_pattern` will always evaluate to false
calling `regenerateRoofingFillAndInnerInfill` without making changes in `skin_part` will not result in different `roof_fill` of `skin_fill` areas.

CURA-9625

Ultimaker/CuraEngine,Ultimaker/CuraEngine