🐞 Remove incorrect -delegates warning

fixes, when server is started with `-delegates` unset:

```
-delegates: arguments should be in the format "delegatedDomain=nameserver", not ""
```

integration_flags_test.go

@@ -173,7 +173,7 @@ var _ = Describe("flags", func() {
 				flags = []string{"-delegates="}
 			})
 			It("should give an informative message", func() {
-				Expect(string(serverSession.Err.Contents())).Should(MatchRegexp(`-delegates: arguments should be in the format "delegatedDomain=nameserver", not ""`))
+				Expect(string(serverSession.Err.Contents())).Should(Not(MatchRegexp(`-delegates`)))
 			})
 		})
 		When("the arguments are mangled", func() {