Remove indentation in text template for markdown files

[pdashk]

Expected Behavior

Output of pdoc.Module().text() generates a markdown file where the headings are not indented. Indentation in markdown creates block quotes, which is not the intended purpose the the h3 (###) headings.

Example output:

`Structure(*args, **kwargs)`
:   Common class for all structures.

### Ancestors (in MRO)

* core.StructuredNode
* core.NodeBase
* properties.PropertyManager

Actual Behavior

text.mako template has indentations for these sections, such that output is:

Example output:

`Structure(*args, **kwargs)`
:   Common class for all structures.

    ### Ancestors (in MRO)

    * core.StructuredNode
    * core.NodeBase
    * properties.PropertyManager

Steps to Reproduce

Run pdoc -o in command line without --html flag to create `.md files.

Additional info

• pdoc version: 0.10.0