Use a regex to fix badly aligned captions

Author: SamantazFox

src/invidious/routes/api/v1/videos.cr

@@ -130,7 +130,13 @@ module Invidious::Routes::API::V1::Videos
         end
       end
     else
+      # Some captions have "align:[start/end]" and "position:[num]%"
+      # attributes. Those are causing issues with VideoJS, which is unable
+      # to properly align the captions on the video, so we remove them.
+      #
+      # See: https://github.com/iv-org/invidious/issues/2391
       webvtt = YT_POOL.client &.get("#{url}&format=vtt").body
+        .gsub(/([0-9:.]+ --> [0-9:.]+).+/, "\\1")
     end
 
     if title = env.params.query["title"]?