DOC: Fix python code error in enhancingperf

[EunSeop]

Problem description

This screenshot is in pandas 0.25.0 documentation, https://pandas.pydata.org/pandas-docs/stable/user_guide/enhancingperf.html#using-ndarray

Current code is

.. ipython:: python

   %prun -l 4 apply_integrate_f(df['a'].to_numpy(),
                                df['b'].to_numpy(),
                                df['N'].to_numpy())

%prun takes only single line, so it can be

.. ipython:: python
   %prun -l 4 apply_integrate_f(df['a'].to_numpy(), df['b'].to_numpy(), df['N'].to_numpy())

or use %%prun

.. ipython:: python
   %%prun -l 4 apply_integrate_f(df['a'].to_numpy(),
                                df['b'].to_numpy(),
                                df['N'].to_numpy())

Expected Output

Output of pd.show_versions()

In [1]: import pandas as pd;pd.show_versions()

INSTALLED VERSIONS

commit : 5b0a2a6
python : 3.6.7.final.0
python-bits : 64
OS : Linux
OS-release : 4.15.0-54-generic
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 0.25.0+191.g5b0a2a6e3.dirty
numpy : 1.17.0
pytz : 2019.2
dateutil : 2.8.0
pip : 19.2.2
setuptools : 41.1.0
Cython : 0.29.13
pytest : 5.1.0
hypothesis : 4.32.3
sphinx : 1.8.5
blosc : 1.8.1
feather : None
xlsxwriter : None
lxml.etree : 4.4.1
html5lib : 1.0.1
pymysql : None
psycopg2 : None
jinja2 : 2.10.1
IPython : 7.7.0
pandas_datareader: None
bs4 : 4.8.0
bottleneck : 1.2.1
fastparquet : 0.3.2
gcsfs : None
lxml.etree : 4.4.1
matplotlib : 3.1.1
numexpr : 2.7.0
odfpy : None
openpyxl : 2.6.2
pandas_gbq : None
pyarrow : 0.14.1
pytables : None
s3fs : None
scipy : 1.3.1
sqlalchemy : None
tables : 3.5.2
xarray : None
xlrd : None
xlwt : None
xlsxwriter : None