Keep MEDIA_URL just in case

- This may be removed when the new theme context is implemented
https://docs.readthedocs.io/en/latest/design/theme-context.html

Author: davidfischer

readthedocs/doc_builder/templates/doc_builder/conf.py.tmpl

@@ -76,6 +76,7 @@ context = {
     'html_theme': html_theme,
     'current_version': "{{ version.verbose_name }}",
     'version_slug': "{{ version.slug }}",
+    'MEDIA_URL': "{{ settings.MEDIA_URL }}",
     'STATIC_URL': "{{ settings.STATIC_URL }}",
     'PRODUCTION_DOMAIN': "{{ settings.PRODUCTION_DOMAIN }}",
     'versions': [{% for version in versions %}