Remove unnecessary type from challenge response

acme4j-client/src/main/java/org/shredzone/acme4j/challenge/Challenge.java

@@ -160,7 +160,7 @@ public class Challenge extends AcmeResource {
      *            {@link JSONBuilder} to copy the response to
      */
     protected void respond(JSONBuilder cb) {
-        cb.put(KEY_TYPE, getType());
+        // Do nothing here...
     }
 
     /**

acme4j-client/src/test/java/org/shredzone/acme4j/challenge/ChallengeTest.java

@@ -140,7 +140,7 @@ public class ChallengeTest {
         JSONBuilder cb = new JSONBuilder();
         challenge.respond(cb);
 
-        assertThat(cb.toString(), sameJSONAs("{\"type\"=\"generic-01\"}"));
+        assertThat(cb.toString(), sameJSONAs("{}"));
     }
 
     /**

acme4j-client/src/test/resources/json/triggerHttpChallengeRequest.json

@@ -1,4 +1,3 @@
 {
-  "type": "http-01",
   "keyAuthorization": "IlirfxKKXAsHtmzK29Pj8A.HnWjTDnyqlCrm6tZ-6wX-TrEXgRdeNu9G71gqxSO6o0"
 }