Fix typo (#342)

Co-authored-by: holly1238 <77758406+holly1238@users.noreply.github.com>

Author: nzw0301

beginner_source/nlp/README.txt

@@ -14,9 +14,9 @@ Deep Learning for NLP with Pytorch
 	https://pytorch.org/tutorials/beginner/nlp/word_embeddings_tutorial.html
 
 4. sequence_models_tutorial.py
-	Sequence Models and Long-Short Term Memory Networks
+	Sequence Models and Long Short-Term Memory Networks
 	https://pytorch.org/tutorials/beginner/nlp/sequence_models_tutorial.html
 
 5. advanced_tutorial.py
 	Advanced: Making Dynamic Decisions and the Bi-LSTM CRF
-	https://pytorch.org/tutorials/beginner/nlp/advanced_tutorial.html
+	https://pytorch.org/tutorials/beginner/nlp/advanced_tutorial.html

beginner_source/nlp/sequence_models_tutorial.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 r"""
-Sequence Models and Long-Short Term Memory Networks
+Sequence Models and Long Short-Term Memory Networks
 ===================================================
 
 At this point, we have seen various feed-forward networks. That is,