Use HttpMessageNotWritableException instead of ISE

As a follow-up to the recent commit #37f9ce, this change replaces the
raised IllegalStateException with HttpMessageNotWritableException.

See gh-23205

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/AbstractMessageConverterMethodProcessor.java

@@ -176,6 +176,9 @@ public abstract class AbstractMessageConverterMethodProcessor extends AbstractMe
 	 * @throws IOException thrown in case of I/O errors
 	 * @throws HttpMediaTypeNotAcceptableException thrown when the conditions indicated
 	 * by the {@code Accept} header on the request cannot be met by the message converters
+	 * @throws HttpMessageNotWritableException thrown if a given message cannot
+	 * be written by a converter, or if the content-type chosen by the server
+	 * has no compatible converter.
 	 */
 	@SuppressWarnings({"rawtypes", "unchecked"})
 	protected <T> void writeWithMessageConverters(@Nullable T value, MethodParameter returnType,
@@ -306,7 +309,7 @@ public abstract class AbstractMessageConverterMethodProcessor extends AbstractMe
 
 		if (body != null) {
 			if (isContentTypePreset) {
-				throw new IllegalStateException(
+				throw new HttpMessageNotWritableException(
 						"No converter for [" + valueType + "] with preset Content-Type '" + contentType + "'");
 			}
 			throw new HttpMediaTypeNotAcceptableException(this.allSupportedMediaTypes);