migrated to newer version of lightning

[aryankeluskar]

Using the official migration guide available at this PR. The validation_epoch_end function was replaced with on_validation_epoch_end, so I updated the DeepBLAST class to ensure compatibility with pytorch-lightening and fixed the following error:

NotImplementedError: Support for `validation_epoch_end` has been removed in v2.0.0. 
`DeepBLAST` implements this method. You can use the `on_validation_epoch_end` hook instead. 
To access outputs, save them in-memory as instance attributes.

Additionally, I resolved a deprecation warning caused by the use of np.bool by switching to bool

[mortonjt]

Thanks, I'll merge and note that we are missing the validation metrics in a separate issue.