DOC: add print statement in to_latex example

[jorisvandenbossche]

The docstring of to_latext shows a small example (https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.to_latex.html) as

>>> df = pd.DataFrame({'name': ['Raphael', 'Donatello'],
...                    'mask': ['red', 'purple'],
...                    'weapon': ['sai', 'bo staff']})
>>> df.to_latex(index=False) # doctest: +NORMALIZE_WHITESPACE
'\\begin{tabular}{lll}\n\\toprule\n      name &    mask &    weapon
\\\\\n\\midrule\n   Raphael &     red &       sai \\\\\n Donatello &
 purple &  bo staff \\\\\n\\bottomrule\n\\end{tabular}\n'

I think it would be nice to also add a print statement like print(df.to_latex(index=False))(typically you want to be able to copy it to your tex file, and so you first need to print it to have something you can copy paste)