Save exclude_from_weight_decay in config for LAMB

[leondgarse]

Before:

import tensorflow_addons as tfa
mm = keras.models.Sequential([keras.layers.Input([32, 32, 3]), keras.layers.Flatten(), keras.layers.Dense(10)])
mm.compile(optimizer=tfa.optimizers.LAMB(learning_rate=0.1, weight_decay_rate=0.02, exclude_from_weight_decay=['/gamma', '/beta']))
mm.save('aa.h5')
bb = keras.models.load_model('aa.h5')
print(bb.optimizer.exclude_from_weight_decay, bb.optimizer.exclude_from_layer_adaptation)
# None, None

After:

import tensorflow_addons as tfa
mm = keras.models.Sequential([keras.layers.Input([32, 32, 3]), keras.layers.Flatten(), keras.layers.Dense(10)])
mm.compile(optimizer=tfa.optimizers.LAMB(learning_rate=0.1, weight_decay_rate=0.02, exclude_from_weight_decay=['/gamma', '/beta']))
mm.save('aa.h5')
bb = keras.models.load_model('aa.h5')
print(bb.optimizer.exclude_from_weight_decay, bb.optimizer.exclude_from_layer_adaptation)
# ['/gamma', '/beta'] ['/gamma', '/beta']

Description

Brief Description of the PR:

Fixes # (issue)

Type of change

• Bug fix
• New Tutorial
• Updated or additional documentation
• Additional Testing
• New Activation and the changes conform to the activation contribution guidelines
• New Callback and the changes conform to the callback contribution guidelines
• New Image addition and the changes conform to the image op contribution guidelines
• New Layer and the changes conform to the layer contribution guidelines
• New Loss and the changes conform to the loss contribution guidelines
• New Metric and the changes conform to the metric contribution guidelines
• New Optimizer and the changes conform to the optimizer contribution guidelines
• New RNN Cell and the changes conform to the rnn contribution guidelines
• New Seq2seq addition and the changes conform to the seq2seq contribution guidelines
• New Text addition and the changes conform to the text op contribution guidelines

Checklist:

• I've properly formatted my code according to the guidelines
  • By running Black + Flake8
  • By running pre-commit hooks
• This PR addresses an already submitted issue for TensorFlow Addons
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• This PR contains modifications to C++ custom-ops

How Has This Been Tested?

If you're adding a bugfix or new feature please describe the tests that you ran to verify your changes:
*

[bot-of-gabrieldemarmiesse]

@junjiek

You are owner of some files modified in this pull request.
Would you kindly review the changes whenever you have the time to?
Thank you very much.