Fix assertion description

Author: RafaelKayumov

Project/JSONAPITests/JSONAPITests.m

@@ -247,7 +247,7 @@ - (void)testEmptyRelationship {
 
     NewsFeedPostResource *testPost = jsonAPI.resource;
 
-    XCTAssertNil(testPost.publisher, @"Test post's attachments should not be nil");
+    XCTAssertNil(testPost.publisher, @"Test post's publisher should be nil");
 
     XCTAssertNotNil(testPost.attachments, @"Test post's attachments should not be nil");
     XCTAssertEqual(testPost.attachments.count, 1, @"Test post's attachments should contain 1 object");