Initialize Map with correct size in RequestPredicates

Fix another instance where a LinkedHashMap was initialized with an initial
capacity that would always cause a resize / rehash to occur. Switch to
CollectionUtils.newLinkedHashMap to size the map appropiately for the expected
number of items.

Closes gh-32215

Author: kilink

spring-webmvc/src/main/java/org/springframework/web/servlet/function/RequestPredicates.java

@@ -1237,7 +1237,7 @@ private static Map<String, Object> mergeAttributes(ServerRequest request, Map<St
 			PathPattern oldPathPattern = (PathPattern) request.attribute(RouterFunctions.MATCHING_PATTERN_ATTRIBUTE)
 					.orElse(null);
 
-			Map<String, Object> result = new LinkedHashMap<>(2);
+			Map<String, Object> result = CollectionUtils.newLinkedHashMap(2);
 			result.put(RouterFunctions.URI_TEMPLATE_VARIABLES_ATTRIBUTE, mergeMaps(oldPathVariables, newPathVariables));
 			result.put(RouterFunctions.MATCHING_PATTERN_ATTRIBUTE, mergePatterns(oldPathPattern, newPathPattern));
 			return result;