Avoid duplicate addition of void.class in ClassUtils

This commit avoids duplicate addition of void.class to the temporary
primitiveTypes Set in the static initialization block in ClassUtils.

Closes gh-25128

spring-core/src/main/java/org/springframework/util/ClassUtils.java

@@ -141,7 +141,6 @@ public abstract class ClassUtils {
 		primitiveTypes.addAll(primitiveWrapperTypeMap.values());
 		Collections.addAll(primitiveTypes, boolean[].class, byte[].class, char[].class,
 				double[].class, float[].class, int[].class, long[].class, short[].class);
-		primitiveTypes.add(void.class);
 		for (Class<?> primitiveType : primitiveTypes) {
 			primitiveTypeNameMap.put(primitiveType.getName(), primitiveType);
 		}