Update ex2_3.md

unnecessary space after a tab (from 5 to 4 spaces)

Exercises/ex2_3.md

@@ -220,7 +220,7 @@ Watch what happens if you do the for-loop again:
 
 ```python
 >>> for n in squares:
-         print(n)
+        print(n)
 
 >>>
 ```
@@ -291,7 +291,7 @@ False
 >>>
 ```
 
-Here is an subtle use of a generator expression in making comma
+Here is a subtle use of a generator expression in making comma
 separated values:
 
 ```python