Remove HTTP parts workaround for Resin

A workaround was added for the Resin Servlet container in gh-13937.
This avoids attempting to delete parts that are not named, because the
`part.delete()` call would fail for non-file entries. This can be
problematic for files that are unnamed as they might not be removed by
the Framework.

This commit removes this workaround as Resin is not supported anymore.

Fixes gh-33511

Author: bclozel

spring-web/src/main/java/org/springframework/web/multipart/support/StandardServletMultipartResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -116,13 +116,10 @@ public MultipartHttpServletRequest resolveMultipart(HttpServletRequest request)
 	public void cleanupMultipart(MultipartHttpServletRequest request) {
 		if (!(request instanceof AbstractMultipartHttpServletRequest abstractMultipartHttpServletRequest) ||
 				abstractMultipartHttpServletRequest.isResolved()) {
-			// To be on the safe side: explicitly delete the parts,
-			// but only actual file parts (for Resin compatibility)
+
 			try {
 				for (Part part : request.getParts()) {
-					if (request.getFile(part.getName()) != null) {
-						part.delete();
-					}
+					part.delete();
 				}
 			}
 			catch (Throwable ex) {