Clean up OpenAPI annotations on PUT /v1/challenge

* Remove 413 response since we no longer send it
* Add missing 428 response for when invalid captcha is submitted

service/src/main/java/org/whispersystems/textsecuregcm/controllers/ChallengeController.java

@@ -73,9 +73,7 @@ public class ChallengeController {
           AnswerCaptchaChallengeRequest.class}))})
   )
   @ApiResponse(responseCode = "200", description = "Indicates the challenge proof was accepted")
-  @ApiResponse(responseCode = "413", description = "Too many attempts", headers = @Header(
-      name = "Retry-After",
-      description = "If present, an positive integer indicating the number of seconds before a subsequent attempt could succeed"))
+  @ApiResponse(responseCode = "428", description = "Submitted captcha token is invalid")
   @ApiResponse(responseCode = "429", description = "Too many attempts", headers = @Header(
       name = "Retry-After",
       description = "If present, an positive integer indicating the number of seconds before a subsequent attempt could succeed"))