Refinement for ResolvableType JSON header

Fix a logic in the `JsonToObjectTransformer.obtainResolvableTypeFromHeadersIfAny`
when we have both `JsonHeaders.RESOLVABLE_TYPE` and `JsonHeaders.TYPE_ID`
and `JsonHeaders.RESOLVABLE_TYPE` header is valid `ResolvableType`, so
`JsonHeaders.TYPE_ID` doesn't override its value to return

Author: artembilan

spring-integration-core/src/main/java/org/springframework/integration/json/JsonToObjectTransformer.java

@@ -148,7 +148,7 @@ protected Object doTransform(Message<?> message) {
 	private ResolvableType obtainResolvableTypeFromHeadersIfAny(MessageHeaders headers) {
 		Object valueType = headers.get(JsonHeaders.RESOLVABLE_TYPE);
 		Object typeIdHeader = headers.get(JsonHeaders.TYPE_ID);
-		if (typeIdHeader != null) {
+		if (!(valueType instanceof ResolvableType) && typeIdHeader != null) {
 			Class<?> targetClass = getClassForValue(typeIdHeader);
 			Class<?> contentClass = null;
 			Class<?> keyClass = null;