fix style check warnings

[shibukawa]

Subject: fix style check warnings on master branch

Feature or Bugfix

• Bugfix

Detail

doc/ext/example_google.py:127: DeprecationWarning: invalid escape sequence \*
  """
doc/ext/example_numpy.py:160: DeprecationWarning: invalid escape sequence \*
  """
tests/test_build_latex.py:494: DeprecationWarning: invalid escape sequence \h
  'footnote in table not in header\n%\n\\end{footnote}\n\\\\\n\hline\n'
tests/test_ext_napoleon_docstring.py:296: DeprecationWarning: invalid escape sequence \[
  """
tests/test_ext_napoleon_docstring.py:313: DeprecationWarning: invalid escape sequence \[
  """

[tk0miya]

LGTM!