Update 02.2.md

Quick fix, sentence had a typo. Removed extra 'a'.

en/02.2.md

@@ -244,7 +244,7 @@ The reason that Go is concise because it has some default behaviors.
 
 ### array
 
-`array` is an array obviously, we define a one as follows.
+`array` is an array obviously, we define one as follows.
 
 	var arr [n]type