Fix AuthorizationManager T Nullability

Previously AuthorizationManager declared the generic's Nullability
incorrectly. This commit marks it properly.

Closes gh-17667

Author: rwinch

core/src/main/java/org/springframework/security/authorization/AuthorizationManager.java

@@ -31,7 +31,7 @@
  * @author Evgeniy Cheban
  */
 @FunctionalInterface
-public interface AuthorizationManager<@Nullable T> {
+public interface AuthorizationManager<T extends @Nullable Object> {
 
 	/**
 	 * Determines if access should be granted for a specific authentication and object.