Fixed as per solution at https://github.com/JamesNK/Newtonsoft.Json/issues/874.
Note that due to the use of `JsonExtensionDataAttribute` it's not
feasible to change the actual specification to `JValue` in the
`Dictionary`.
In discussion with the osu-web team, it may be worthwhile to change the cursor
to a string format where parsing is not required at our end. We could already
do this in fact, but there are tests that rely on it being a `JToken` so the
switch to `JValue` seems like the easier path right now.
