Fix too high mask_multiplier
Fix too high mask_multiplier

The value of mask_multiplier was set too high compared to the intended change,
the current value gives too much ringing, 2 works well and was the intended
value.

libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl