Switch FaviconRequestHandler visibility to package private

Closes gh-16250

Author: mrifni

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration.java

@@ -449,10 +449,9 @@ private List<Resource> resolveFaviconLocations() {
 
 		}
 
-		private static final class FaviconRequestHandler
-				extends ResourceHttpRequestHandler {
+		static final class FaviconRequestHandler extends ResourceHttpRequestHandler {
 
-			private FaviconRequestHandler(List<Resource> locations) {
+			FaviconRequestHandler(List<Resource> locations) {
 				setLocations(locations);
 			}