Clean NettyWebServer tests

Remove ununsed tests after gh-9698

spring-boot/src/test/java/org/springframework/boot/web/embedded/netty/NettyWebServerTests.java

-/*
- * Copyright 2012-2017 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.springframework.boot.web.embedded.netty;
-
-import org.junit.Test;
-
-/**
- * Tests for {@link NettyWebServer}.
- *
- * @author Madhura Bhave
- */
-public class NettyWebServerTests {
-
-	private NettyWebServer server;
-
-	@Test
-	public void stopWhenLatchIsNullShouldNotThrowException() throws Exception {
-		this.server = new NettyWebServer(null, null);
-		this.server.stop();
-	}
-
-}