Hardcoded bucket_step overrides configurable parameter

Hey, just noticed that bucket_step is hardcoded to 64 here:
https://github.com/kohya-ss/sd-scripts/blob/0778dd9b1df0d6aa33287ded3ce4195f3d03251b/train_network.py#L127-L130
But there's already a configurable parameter for this elsewhere in the code. This kinda defeats the purpose of having it configurable in the first place.

Personally, I find 32 way more practical than 64. Any particular reason for this change? Any chance we can bring back configurability?

Start in train_network.py around lines 127–130 and trace the existing configurable bucket_step parameter elsewhere in the code. Confirm where the hardcoded value overrides it, then verify that the configured value is honored, including values such as 32.

Written by the indexing model from the issue text.