html scrubbing policies: restrict img tags to http/https only for mediaproxy compatibility

lib/pleroma/html.ex

@@ -63,7 +63,8 @@ defmodule Pleroma.HTML.Scrubber.TwitterText do
   @allow_inline_images Keyword.get(@markup, :allow_inline_images)
 
   if @allow_inline_images do
-    Meta.allow_tag_with_uri_attributes("img", ["src"], @valid_schemes)
+    # restrict img tags to http/https only, because of MediaProxy.
+    Meta.allow_tag_with_uri_attributes("img", ["src"], ["http", "https"])
 
     Meta.allow_tag_with_these_attributes("img", [
       "width",
@@ -113,7 +114,8 @@ defmodule Pleroma.HTML.Scrubber.Default do
   @allow_inline_images Keyword.get(@markup, :allow_inline_images)
 
   if @allow_inline_images do
-    Meta.allow_tag_with_uri_attributes("img", ["src"], @valid_schemes)
+    # restrict img tags to http/https only, because of MediaProxy.
+    Meta.allow_tag_with_uri_attributes("img", ["src"], ["http", "https"])
 
     Meta.allow_tag_with_these_attributes("img", [
       "width",