Don't allow `.ogg` as a valid video extension

`.ogg` is for music files.
Signed-off-by: Rémy Coutable <remy@rymai.me>

config/initializers/mime_types.rb

@@ -11,4 +11,4 @@ Mime::Type.register_alias "text/html",  :md
 
 Mime::Type.register "video/mp4",  :mp4, [], [:m4v, :mov]
 Mime::Type.register "video/webm", :webm
-Mime::Type.register "video/ogg",  :ogv, [], [:ogg]
+Mime::Type.register "video/ogg",  :ogv

doc/markdown/markdown.md

@@ -286,7 +286,7 @@ Task lists can only be created in descriptions, not in titles. Task item state c
 
 Image tags with a video extension are automatically converted to a video player.
 
-The valid video extensions are `.mp4`, `.m4v`, `.mov`, `.webm`, `.ogv`, and `.ogg`.
+The valid video extensions are `.mp4`, `.m4v`, `.mov`, `.webm`, and `.ogv`.
 
     Here's a sample video: