disgord: Incorrect ratelimit handling for adding reactions

Describe the bug Quick successive CreateReaction calls result in some erroring out with an httd.ErrREST error containing a ratelimit error.

Expected behavior The ratelimit for reactions should be handled correctly, and should retry instead of erroring out.

Error messages

*httd.ErrREST
You are being rate limited. ---- {
  "global": false, 
  "message": "You are being rate limited.", 
  "retry_after": 155
}

Desktop (please complete the following information):

• Golang version: 1.13
• Using Go modules? yes
• Disgord version? v0.16.3
• Connected to the gateway before using REST methods? yes

Additional context I have CancelRequestWhenRateLimited set to false.