Polish SAML2 principal classes

Update @since

Issue: gh-7681

saml2/saml2-service-provider/src/main/java/org/springframework/security/saml2/provider/service/authentication/Saml2AuthenticatedPrincipal.java

@@ -22,7 +22,7 @@ import org.springframework.security.core.AuthenticatedPrincipal;
  * Saml2 representation of an {@link AuthenticatedPrincipal}.
  *
  * @author Clement Stoquart
- * @since 5.3
+ * @since 5.2.2
  */
 public interface Saml2AuthenticatedPrincipal extends AuthenticatedPrincipal {
 }

saml2/saml2-service-provider/src/main/java/org/springframework/security/saml2/provider/service/authentication/SimpleSaml2AuthenticatedPrincipal.java

@@ -22,7 +22,7 @@ import java.io.Serializable;
  * Default implementation of a {@link Saml2AuthenticatedPrincipal}.
  *
  * @author Clement Stoquart
- * @since 5.3
+ * @since 5.2.2
  */
 class SimpleSaml2AuthenticatedPrincipal implements Saml2AuthenticatedPrincipal, Serializable {