fix according to comment

word2vec/README.en.md

@@ -263,7 +263,7 @@ Ethird = wordemb(thirdword)
 Efourth = wordemb(fourthword)
 ```
 
-- Concat n-1 word embedding vectors into a single feature vector.
+- Concatenate n-1 word embedding vectors into a single feature vector.
 
 ```python
 contextemb = paddle.layer.concat(input=[Efirst, Esecond, Ethird, Efourth])

word2vec/index.en.html

@@ -305,7 +305,7 @@ Ethird = wordemb(thirdword)
 Efourth = wordemb(fourthword)
 ```
 
-- Concat n-1 word embedding vectors into a single feature vector.
+- Concatenate n-1 word embedding vectors into a single feature vector.
 
 ```python
 contextemb = paddle.layer.concat(input=[Efirst, Esecond, Ethird, Efourth])