lr scheduler is not optional

[felipemello1]

currently the recipes expect as lr scheduler. If deleted from the config, it crashes. This shouldnt be the case. If the config doesnt provide a scheduler, we should just not update it.

[SalmanMohammadi]

I believe this PR added optional support for the LR scheduler in the FFT recipe which we could copy over #1350.

[felipemello1]

closing in favor of #2021