When a POST request returns a 302 redirect, follow the redirect with a
GET request instead of with a POST request.
HTTP standards leave it unspecified whether a POST request that returns
a 302 redirect should be followed with a GET or with a POST. A GET is
what most browsers use, which means it's what most servers expect.
Fixes the /tagme Discord command not working because when we uploaded
the image to DeepDanbooru, the POST request returned a 302 redirect,
which the server expected us to follow with a GET, not with a POST.
Ref:
* https://stackoverflow.com/questions/17605915/what-is-the-correct-behavior-expected-of-an-http-post-302-redirect-to-get
e2704f6a7b