update extractor test results

- certain posts on Instagram now return
  https://static.cdninstagram.com/rsrc.php/null.jpg
  for public users
- MangaDex is deploying its new MangaDex@Home network similar to
  exhentai's Hentai@Home
- realbooru has a new site layout, but the underlying booru API still
  works like before

test/test_results.py

@@ -31,9 +31,7 @@ TRAVIS_SKIP = {
 
 # temporary issues, etc.
 BROKEN = {
-    "e621",
     "imagevenue",
-    "jaiminisbox",
     "photobucket",
     "worldthree",
 }