Remove disabled wiki plugin

So apparently, "Image Embedding Extension for Python-Markdown" was never
actually enabled. When it was introduced [1], it was already commented
out!?

[1] 93d15d15

lms/djangoapps/course_wiki/plugins/markdownedx/mdx_image.py

-#!/usr/bin/env python
-'''
-Image Embedding Extension for Python-Markdown
-======================================
-
-Converts lone links to embedded images, provided the file extension is allowed.
-
-Ex:
-    http://www.ericfehse.net/media/img/ef/blog/django-pony.jpg
-    becomes
-    <img src="http://www.ericfehse.net/media/img/ef/blog/django-pony.jpg">
-
-    mypic.jpg   becomes    <img src="/MEDIA_PATH/mypic.jpg">
-
-Requires Python-Markdown 1.6+
-'''
-
-import simplewiki.settings as settings
-
-import markdown
-try:
-    # Markdown 2.1.0 changed from 2.0.3. We try importing the new version first,
-    # but import the 2.0.3 version if it fails
-    from markdown.util import etree
-except:
-    from markdown import etree
-
-
-class ImageExtension(markdown.Extension):
-    def __init__(self, configs):
-        for key, value in configs:
-            self.setConfig(key, value)
-
-    def add_inline(self, md, name, klass, re):
-        pattern = klass(re)
-        pattern.md = md
-        pattern.ext = self
-        md.inlinePatterns.add(name, pattern, "<reference")
-
-    def extendMarkdown(self, md, md_globals):
-        self.add_inline(md, 'image', ImageLink,
-                        r'^(?P<proto>([^:/?#])+://)?(?P<domain>([^/?#]*)/)?(?P<path>[^?#]*\.(?P<ext>[^?#]{3,4}))(?:\?([^#]*))?(?:#(.*))?$')
-
-
-class ImageLink(markdown.inlinepatterns.Pattern):
-    def handleMatch(self, m):
-        img = etree.Element('img')
-        proto = m.group('proto') or "http://"
-        domain = m.group('domain')
-        path = m.group('path')
-        ext = m.group('ext')
-
-        # A fixer upper
-        if ext.lower() in settings.WIKI_IMAGE_EXTENSIONS:
-            if domain:
-                src = proto + domain + path
-            elif path:
-                # We need a nice way to source local attachments...
-                src = "/wiki/media/" + path + ".upload"
-            else:
-                src = ''
-            img.set('src', src)
-        return img
-
-
-def makeExtension(configs=None):
-    return ImageExtension(configs=configs)
-
-if __name__ == "__main__":
-    import doctest
-    doctest.testmod()

lms/djangoapps/course_wiki/plugins/markdownedx/wiki_plugin.py

@@ -12,7 +12,6 @@ class ExtendMarkdownPlugin(BasePlugin):
     """
 
     markdown_extensions = [mdx_circuit.CircuitExtension(configs={}),
-                           #mdx_image.ImageExtension() , #This one doesn't work. Tries to import simplewiki.settings
                            mdx_mathjax.MathJaxExtension(configs={}),
                            mdx_video.VideoExtension(configs={})]