Add a missing test case for ObjectUtils#unwrapOptional

Closes gh-33618

Author: sdeleuze

spring-core/src/test/java/org/springframework/util/ObjectUtilsTests.java

@@ -1119,6 +1119,7 @@ private static String prefix(Class<?> clazz) {
 	void unwrapOptional() {
 
 		assertThat(ObjectUtils.unwrapOptional(null)).isNull();
+		assertThat(ObjectUtils.unwrapOptional("some value")).isEqualTo("some value");
 		assertThat(ObjectUtils.unwrapOptional(Optional.empty())).isNull();
 		assertThat(ObjectUtils.unwrapOptional(Optional.of("some value"))).isEqualTo("some value");