CAS-14815: Fix mask threshold default from 0.99 to 0.9 to match multi-scale clean
setInitScaleMasks() in AspMatrixCleaner had a default maskThreshold of 0.99
while multi-scale clean uses 0.9.
The in-code comment already said "10% overlap allowed, hence 0.9" but the
actual default was 0.99 — a 10x stricter threshold.
With 0.99, scale masks for larger Gaussians are heavily eroded near mask
boundaries, causing ASP with auto-multithresh to leave residuals around
components whose large-scale wings fall outside the shrunken scale mask.
Setting 0.9 aligns ASP behavior with multi-scale clean.
