Update Sphinx config for markdown handling

The config format has changed in v3.0 in the handling of markdown.

See https://www.sphinx-doc.org/en/master/usage/markdown.html.

Change-Id: I3f2dad962824e1d5f410f8420795c68715b03635

docs/source/build_instructions.md

@@ -67,12 +67,10 @@ Download the
 [depot_tools bundle](https://storage.googleapis.com/chrome-infra/depot_tools.zip)
 and extract it somewhere.
 
-*** note
-**Warning:** **DO NOT** use drag-n-drop or copy-n-paste extract from Explorer,
+**WARNING: DO NOT** use drag-n-drop or copy-n-paste extract from Explorer,
 this will not extract the hidden “.git” folder which is necessary for
 depot_tools to autoupdate itself. You can use “Extract all…” from the context
 menu though.
-***
 
 Add depot_tools to the start of your PATH (must be ahead of any installs of
 Python). Assuming you unzipped the bundle to C:\src\depot_tools, open:

docs/source/conf.py

@@ -16,8 +16,6 @@ add these directories to sys.path here. If the directory is relative to the
 documentation root, use os.path.abspath to make it absolute, like shown here.
 """
 
-from recommonmark.parser import CommonMarkParser
-
 # sys.path.append('breathe/')
 
 # -- General configuration ------------------------------------------------
@@ -36,6 +34,7 @@ extensions = ['sphinx.ext.autodoc',
               'sphinx.ext.viewcode',
               'sphinx.ext.githubpages',
               'sphinxcontrib.plantuml',
+              'recommonmark',
               'cloud_sptheme.ext.table_styling',
               'breathe']
 
@@ -47,10 +46,6 @@ breathe_default_members = ('members',)
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
 
-source_parsers = {
-    '.md': CommonMarkParser,
-}
-
 # The suffix(es) of source filenames.
 # You can specify multiple suffix as a list of string:
 source_suffix = ['.rst', '.md']