Start building against Spring LDAP 2.4.0-RC1 snapshots

See gh-30606

spring-boot-project/spring-boot-dependencies/build.gradle

@@ -1754,7 +1754,7 @@ bom {
 			]
 		}
 	}
-	library("Spring LDAP", "2.4.0-M2") {
+	library("Spring LDAP", "2.4.0-SNAPSHOT") {
 		prohibit("[3.0.0-M1,)") {
 			because "it uses Spring Framework 6"
 		}