### Description

I got following error
```
[2021-11-09, 08:25:30 UTC] {base.py:70} INFO - Using connection to: id: rdb_conn_id. Host: rdb, Port: 5432, Schema: configuration, Login: user, Password: ***, extra: {'sslmode': 'allow', 'client_encoding': 'utf8'}
[2021-11-09, 08:25:30 UTC] {taskinstance.py:1703} ERROR - Task failed with exception
Traceback (most recent call last):
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/models/taskinstance.py", line 1332, in _run_raw_task
    self._execute_task_with_callbacks(context)
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/models/taskinstance.py", line 1458, in _execute_task_with_callbacks
    result = self._execute_task(context, self.task)
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/models/taskinstance.py", line 1514, in _execute_task
    result = execute_callable(context=context)
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/operators/python.py", line 151, in execute
    return_value = self.execute_callable()
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/operators/python.py", line 162, in execute_callable
    return self.python_callable(*self.op_args, **self.op_kwargs)
  File "/opt/airflow/dags/repo/dags/run_configuration.py", line 34, in run_job
    dagsUtils.run_step_insert_to_temp_table(tenant, job_name, table_name, job_type)
  File "/opt/airflow/dags/rev-e3db01f68e7979d71d12ae24008a97065db2144f/dags/utils/dag_util.py", line 106, in run_step_insert_to_temp_table
    for df in df_result:
  File "/home/airflow/.local/lib/python3.9/site-packages/pandas/io/sql.py", line 1499, in _query_iterator
    data = result.fetchmany(chunksize)
  File "/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/engine/result.py", line 1316, in fetchmany
    self.connection._handle_dbapi_exception(
  File "/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1514, in _handle_dbapi_exception
    util.raise_(exc_info[1], with_traceback=exc_info[2])
  File "/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/util/compat.py", line 182, in raise_
    raise exception
  File "/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/engine/result.py", line 1311, in fetchmany
    l = self.process_rows(self._fetchmany_impl(size))
  File "/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/engine/result.py", line 1224, in _fetchmany_impl
    return self.cursor.fetchmany(size)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 12: ordinal not in range(128)
```

Try to set `extra` in airflow connection but it does not work
![image](https://user-images.githubusercontent.com/37215642/140909372-20805f0c-aa98-44a7-94c2-419aea176f70.png)


### Use case/motivation

See that `airflow/providers/mysql/hooks` support getting `extra` configs from airflow connection https://github.com/apache/airflow/pull/6816 but not yet for postgresql hook

### Related issues

_No response_

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

airflow/providers/postgres/hooks/postgres.py
#
#
#
import os
from contextlib import closing
from copy import deepcopy
from typing import Iterable, List, Optional, Tuple, Union
import psycopg2
import psycopg2.extensions
import psycopg2.extras
from psycopg2.extensions import connection
from psycopg2.extras import DictCursor, NamedTupleCursor, RealDictCursor
from airflow.hooks.dbapi import DbApiHook
from airflow.models.connection import Connection
CursorType = Union[DictCursor, RealDictCursor, NamedTupleCursor]
class PostgresHook(DbApiHook):