Deprecating p.weight_decay.
Deprecating p.weight_decay.

Users are instructed to use p.l2_regularizer_weight for coupled weight decay, and p.decoupled_weight_decay for decoupled weight decay.

Currently, a deprecation warning is given each time p.weight_decay is set.
No change is expected in the optimizers' behaviors.

PiperOrigin-RevId: 476478795

google/praxis,google/praxis