Sofc Keras Surrogates failing tests

[rundxdi]

Tests on sofc_keras_surrogate.py are failing due to an out-of-date Keras model that needs to be re-generated by someone who knows about the model. A deprecation warning indicating these failures has been added.

[ksbeattie]

Discovered in #1401

[ksbeattie]

This will need to wait for #1401 to be merged before re-generating the model (and other keras related ones).

[lbianchi-lbl]

This should be done independently of #1401 so that #1401 is not held up. A separate PR after #1401 is merged should be created once @AlexNoring recreates the model using the updated (post-#1401) supported version of Keras/Tensorflow.

[AlexNoring]

The SOFC flowsheets in the examples repository no longer use the keras surrogates. I'd suggest we simply remove the files.

[ksbeattie]

@bpaul4 will open a PR addressing this.