pd.read_json() doesn't use utf-8 for a default encoding
#### Code Sample, a copy-pastable example if possible

```python
# if locale.getpreferredencoding() != 'UTF-8'
import pandas as pd

with open('test.json', 'w', encoding='utf-8') as f:
    f.write('{"A": ["АБВГДабвгд가"]}') 
dt2 = pd.read_json('test.json')
print(dt2)
```

```python
# if locale.getpreferredencoding() == 'UTF-8'
import pandas as pd
from unittest import mock

with open('test.json', 'w', encoding='utf-8') as f:
    f.write('{"A": ["АБВГДабвгд가"]}') 
with mock.patch('_bootlocale.getpreferredencoding', return_value='cp949'):
    dt2 = pd.read_json('test.json')
    print(dt2)
```
#### Problem description

According to the [docs](https://pandas-docs.github.io/pandas-docs-travis/reference/api/pandas.read_json.html#pandas.read_json), when `encoding` parameter is not given, **read_json()** uses `utf-8` for a default encoding.

However, when read_json() is called without encoding parameter, it [calls built-in open()](https://github.com/pandas-dev/pandas/blob/5c36aa1305b07b1d6da4c2a63b6d5b9887503699/pandas/io/common.py#L486) method to open a file and [open() uses return value of locale.getpreferredencoding()](https://docs.python.org/3/library/functions.html#open) to determine the encoding which can be something not utf-8 (My test environment was cp949 in Windows10/Korean).

#### Expected Output

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

<details>

INSTALLED VERSIONS
------------------
commit           : None
python           : 3.6.8.final.0
python-bits      : 64
OS               : Linux
OS-release       : 4.15.0-66-generic
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 0.25.3
numpy            : 1.17.4
pytz             : 2019.3
dateutil         : 2.8.1
pip              : 9.0.1
setuptools       : 39.0.1
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : 0.999999999
pymysql          : 0.9.3
psycopg2         : None
jinja2           : None
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : None
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : None
sqlalchemy       : None
tables           : None
xarray           : None
xlrd             : None
xlwt             : None
xlsxwriter       : None
</details>