Fix/punctuation/trainer required for setting test data
# What does this PR do ?

1. Previously `PunctuationCapitalizationModel.set_trainer()` was required before calling `PunctuationCapitalizatoinModel.set_{training,test,validation}_data()`. This is unexpected for users. Now `set_trainer()` call is not required and warnings are shown.
2. Training random seed for batching is now `current_epoch` instead of `global_step`.
3. Typo fix
4. Fix last cell in punctuation notebook tutorial.

**Collection**: nlp

