**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
"""Generates a URL to the Graph View for a TaskInstance."""
    dag_id = attr.get('dag_id')
    task_id = attr.get('task_id')
    execution_date = attr.get('execution_date')
    url = url_for('Airflow.task', dag_id=dag_id, task_id=task_id, execution_date=execution_date.isoformat())
    url_root = url_for(
        'Airflow.graph', dag_id=dag_id, root=task_id, execution_date=execution_date.isoformat()
    )
    return Markup(  
        """
        <span style="white-space: nowrap;">
        <a href="{url}">{task_id}</a>
        <a href="{url_root}" title="Filter on this task and upstream">
        <span class="material-icons" style="margin-left:0;"
            aria-hidden="true">filter_alt</span>
        </a>
        </span>
        """
    ).format(url=url, task_id=task_id, url_root=url_root)
def state_token(state):
    """Returns a formatted string with HTML for a given State"""
    color = State.color(state)
    fg_color = State.color_fg(state)
    return Markup(  
        """
        <span class="label" style="color:{fg_color}; background-color:{color};"
            title="Current State: {state}">{state}</span>
        """
    ).format(color=color, state=state, fg_color=fg_color)
def state_f(attr):