DOC: Change document code prun in a row (pandas-dev#28029)

Author: EunSeop

doc/source/user_guide/enhancingperf.rst

@@ -243,9 +243,9 @@ We've gotten another big improvement. Let's check again where the time is spent:
 
 .. ipython:: python
 
-   %prun -l 4 apply_integrate_f(df['a'].to_numpy(),
-                                df['b'].to_numpy(),
-                                df['N'].to_numpy())
+   %%prun -l 4 apply_integrate_f(df['a'].to_numpy(),
+                                 df['b'].to_numpy(),
+                                 df['N'].to_numpy())
 
 As one might expect, the majority of the time is now spent in ``apply_integrate_f``,
 so if we wanted to make anymore efficiencies we must continue to concentrate our