Series to_json Docstring Updates
#### Problem description

Documentation for [`Series.to_json`](https://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.to_json.html#pandas.Series.to_json) appears to have been copied from `DataFrame.to_json`. 

This documentation ends up misleading the user when the user wants the Series serialised to JSON in a `records` format.

Without any arguments, the method returns a JSON object that already looks like it's formatted as `records`. However, if you do pass `records=True`, `to_json` returns only an array of values in the Series.

#### Code Sample, a copy-pastable example if possible

```python
s = pd.Series([1, 2, 3])
s.to_json()                                                                                                                         
# Out[12]: '{"0":1,"1":2,"2":3}'

s.to_json(orient='records')                                                                                                         
# Out[13]: '[1,2,3]'
```

The documentation of `Series.to_json` should be updated to reflect that this method behaves differently than the one of `DataFrame.to_json`

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

<details>

[paste the output of ``pd.show_versions()`` here below this line]

INSTALLED VERSIONS
------------------
commit: None
python: 3.6.5.final.0
python-bits: 64
OS: Linux
OS-release: 4.4.0-1070-aws
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.23.4
pytest: 3.5.1
pip: 10.0.1
setuptools: 39.1.0
Cython: 0.28.4
numpy: 1.14.5
scipy: 1.1.0
pyarrow: 0.11.1
xarray: None
IPython: 6.4.0
sphinx: 1.7.4
patsy: 0.5.0
dateutil: 2.7.3
pytz: 2018.4
blosc: None
bottleneck: 1.2.1
tables: 3.4.3
numexpr: 2.6.5
feather: None
matplotlib: 2.2.2
openpyxl: 2.5.3
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 1.0.4
lxml: 4.2.1
bs4: 4.6.0
html5lib: 1.0.1
sqlalchemy: 1.2.11
pymysql: None
psycopg2: 2.7.5 (dt dec pq3 ext lo64)
jinja2: 2.10
s3fs: 0.1.6
fastparquet: None
pandas_gbq: None
pandas_datareader: None

</details>
