**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
"""Mixin for filter for UTC time."""
    def apply(self, query, value):
        """Apply the filter."""
        value = timezone.parse(value, timezone=timezone.utc)
        return super().apply(query, value)  
class UtcAwareFilterEqual(UtcAwareFilterMixin, fab_sqlafilters.FilterEqual):  
    """Equality filter for UTC time."""
class UtcAwareFilterGreater(UtcAwareFilterMixin, fab_sqlafilters.FilterGreater):  
    """Greater Than filter for UTC time."""
class UtcAwareFilterSmaller(UtcAwareFilterMixin, fab_sqlafilters.FilterSmaller):  
    """Smaller Than filter for UTC time."""
class UtcAwareFilterNotEqual(UtcAwareFilterMixin, fab_sqlafilters.FilterNotEqual):  
    """Not Equal To filter for UTC time."""
class UtcAwareFilterConverter(fab_sqlafilters.SQLAFilterConverter):  
    """Retrieve conversion tables for UTC-Aware filters."""
    conversion_table = (
        (
            'is_utcdatetime',
            [UtcAwareFilterEqual, UtcAwareFilterGreater, UtcAwareFilterSmaller, UtcAwareFilterNotEqual],
        ),
    ) + fab_sqlafilters.SQLAFilterConverter.conversion_table
class CustomSQLAInterface(SQLAInterface):