Fix delete discussion API

https://docs.gitlab.com/ee/api/discussions.html#delete-a-merge-request-thread-note

src/main/java/org/gitlab4j/api/DiscussionsApi.java

@@ -368,7 +368,7 @@ public class DiscussionsApi extends AbstractApi {
     public void deleteMergeRequestDiscussionNote(Object projectIdOrPath, Integer mergeRequestIid,
             String discussionId, Integer noteId)  throws GitLabApiException {
         delete(Response.Status.OK, null, "projects", getProjectIdOrPath(projectIdOrPath),
-                "merge_requests", mergeRequestIid, "discussions", noteId);
+                "merge_requests", mergeRequestIid, "discussions", discussionId, "notes", noteId);
     }
 
     /**
@@ -754,4 +754,4 @@ public class DiscussionsApi extends AbstractApi {
         delete(Response.Status.OK, null, "projects", getProjectIdOrPath(projectIdOrPath), "issues", issueIid, "discussions", discussionId, "notes", noteId);
     }
 
-}
\ No newline at end of file
+}