message: Fix broken link to arxiv entry for AdamW Optimizer
diff: @@ -356,10 +356,10 @@ class MomentumWOptimizer(DecoupledWeightDecayExtension,
  class AdamWOptimizer(DecoupledWeightDecayExtension, adam.AdamOptimizer):
  """Optimizer that implements the Adam algorithm with weight decay.
  - This is an implementation of the AdamW optimizer described in "Fixing
  - Weight Decay Regularization in Adam" by Loshchilov & Hutter
  + This is an implementation of the AdamW optimizer described in ["Fixing
  + Weight Decay Regularization in Adam" by Loshchilov & Hutter]
  (https://arxiv.org/abs/1711.05101)
  - ([pdf])(https://arxiv.org/pdf/1711.05101.pdf).
  + ([pdf](https://arxiv.org/pdf/1711.05101.pdf)).
  It computes the update step of `train.AdamOptimizer` and additionally decays
  the variable. Note that this is different from adding L2 regularization on
  