DOC:  confusing wording in Dataframe.quantile 'a la'
#### Problem description
`` a la`` is confusing. The same issue I encountered in Series.quantile is in Dataframe.quantile
#21292
https://github.com/pandas-dev/pandas/blob/25e6a21ac5f3a266de97a6dc00170e106215efa1/pandas/core/frame.py#L7249-L7253
#### Expected Output

#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit: None
python: 3.5.2.final.0
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 94 Stepping 3, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.23.4
pytest: 2.9.2
pip: 9.0.1
setuptools: 40.0.0
Cython: 0.28.4
numpy: 1.14.2
scipy: 1.0.0
pyarrow: None
xarray: None
IPython: 5.1.0
sphinx: 1.4.6
patsy: 0.4.1
dateutil: 2.6.1
pytz: 2017.3
blosc: None
bottleneck: 1.1.0
tables: 3.2.2
numexpr: 2.6.4
feather: None
matplotlib: 2.1.1
openpyxl: 2.3.2
xlrd: 1.0.0
xlwt: 1.1.2
xlsxwriter: 0.9.3
lxml: 3.6.4
bs4: 4.5.1
html5lib: None
sqlalchemy: 1.0.13
pymysql: None
psycopg2: None
jinja2: 2.8
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None

</details>
