Suppress warnings in tests

This commit suppresses warnings in test classes that were polluting the
Gradle build output.

spring-web/src/test/java/org/springframework/web/client/HttpMessageConverterExtractorTests.java

@@ -126,6 +126,7 @@ public class HttpMessageConverterExtractorTests {
 	}
 
 	@Test
+	@SuppressWarnings("unchecked")
 	public void connectionClose() throws IOException {
 		HttpMessageConverter<String> converter = mock(HttpMessageConverter.class);
 		List<HttpMessageConverter<?>> converters = new ArrayList<HttpMessageConverter<?>>();