Post#normalized_source: fix gelbooru source normalization.

Didn't handle https or md5-based subdirs:

    https://gelbooru.com//images/57/a3/57a3676a63e5cf4ab05463a3a9a953bb.jpg
        ^                        ^^^^^

app/models/post.rb

@@ -436,8 +436,11 @@ class Post < ApplicationRecord
       when %r{\Ahttp://static[1-6]?\.minitokyo\.net/(?:downloads|view)/(?:\d{2}/){2}(\d+)}i
         "http://gallery.minitokyo.net/download/#{$1}"
 
-      when %r{\Ahttp://(?:(?:s?img|cdn|www)\d?\.)?gelbooru\.com/{1,2}(?:images|samples)/\d+/(?:sample_)?(?:[a-f0-9]{32}|[a-f0-9]{40})\.}i
-        "https://gelbooru.com/index.php?page=post&s=list&md5=#{md5}"
+      # https://gelbooru.com//images/ee/5c/ee5c9a69db9602c95debdb9b98fb3e3e.jpeg
+      # http://simg.gelbooru.com//images/2003/edd1d2b3881cf70c3acf540780507531.png
+      # https://simg3.gelbooru.com//samples/0b/3a/sample_0b3ae5e225072b8e391c827cb470d29c.jpg
+      when %r{\Ahttps?://(?:\w+\.)?gelbooru\.com//?(?:images|samples)/(?:\d+|\h\h/\h\h)/(?:sample_)?(?<md5>\h{32})\.}i
+        "https://gelbooru.com/index.php?page=post&s=list&md5=#{$~[:md5]}"
 
       when %r{\Ahttps?://(?:slot\d*\.)?im(?:g|ages)\d*\.wikia\.(?:nocookie\.net|com)/(?:_{2}cb\d{14}/)?([^/]+)(?:/[a-z]{2})?/images/(?:(?:thumb|archive)?/)?[a-f0-9]/[a-f0-9]{2}/(?:\d{14}(?:!|%21))?([^/]+)}i
         subdomain = $1