DOC: fix typo in cookbook.rst (pandas-dev#21635)

Removing the semicolon delimiter at the end of the modified line of code allows the line's output to be displayed.

Author: bgroveben

doc/source/cookbook.rst

@@ -132,7 +132,7 @@ Building Criteria
 
 .. ipython:: python
 
-   newseries = df.loc[(df['BBB'] > 25) | (df['CCC'] >= -40), 'AAA']; newseries;
+   newseries = df.loc[(df['BBB'] > 25) | (df['CCC'] >= -40), 'AAA']; newseries
 
 ...or (with assignment modifies the DataFrame.)