Polish package-info for org.springframework.util

See gh-28411

spring-core/src/main/java/org/springframework/util/package-info.java

@@ -1,6 +1,6 @@
 /**
- * Miscellaneous utility classes, such as String manipulation utilities,
- * and a state holder for paged lists of objects.
+ * Miscellaneous utility classes, such as utilities for working with strings,
+ * classes, collections, reflection, etc.
  */
 @NonNullApi
 @NonNullFields