[Misc] Increase faraday open_timeout

This was previously mistyped which made it fall back to the default of 60 seconds.
Apparently 5 is not enough since there are a few errors on prod for this

config/danbooru_default_config.rb

@@ -581,7 +581,7 @@ module Danbooru
       {
         request: {
           timeout: 10,
-          open_timeout: 5,
+          open_timeout: 10,
         },
         headers: http_headers,
       }