**Apache Airflow version**: 1.10.11

**Environment**: Python 3.7

- **Cloud provider or hardware configuration**:
- **OS** (e.g. from /etc/os-release): PRETTY_NAME="Debian GNU/Linux 10 (buster)"
 (from python3.7-slim-buster docker image)
- **Kernel** (e.g. `uname -a`): Linux 5.4.0-42-generic #46-Ubuntu SMP Fri Jul 10 00:24:02 UTC 2020 x86_64 GNU/Linux
- **Install tools**:
- **Others**:

**What happened**:

Using a markdown formatted table does not work.

**What you expected to happen**:

To be able to see a formated table within DAG view

**How to reproduce it**:

Add a tabular formatted code do dag.doc_md.

Example:

> mytable:
> 
> | a | b | c |
> | ------------- | ------------- | ------------- |
> | a | b | c |

[Table not formatted](https://i.imgur.com/l6JXuWe.png)

**Anything else we need to know**: N/A

airflow/www/utils.py
#
#
#
import json
import time
from urllib.parse import urlencode
import markdown
import sqlalchemy as sqla
from flask import Markup, Response, request, url_for
from flask_appbuilder.forms import FieldConverter
from flask_appbuilder.models.sqla import filters as fab_sqlafilters
from flask_appbuilder.models.sqla.interface import SQLAInterface
from pygments import highlight, lexers
from pygments.formatters import HtmlFormatter  
from airflow.configuration import conf
from airflow.utils import timezone
from airflow.utils.code_utils import get_python_source
from airflow.utils.json import AirflowJsonEncoder
from airflow.utils.state import State
from airflow.www.forms import DateTimeWithTimezoneField
from airflow.www.widgets import AirflowDateTimePickerWidget
DEFAULT_SENSITIVE_VARIABLE_FIELDS = [
    'password',
    'secret',