Update NodeJS to 24.15

This commit declares a NodeJS value whereas previously,
Antora would use the latest LTS version. When it updated to
Node 24.16, site production stopped, possibly due to
nodejs/node@e95570c054.

Either way, it is helpful to have a pinned version in order
to stabilize builds, allowing us to update it in an orderly
fashion like other dependencies.

Issue gh-1512

Signed-off-by: Josh Cummings <3627351+jzheaux@users.noreply.github.com>

Author: jzheaux

build.gradle

@@ -24,6 +24,10 @@ apply plugin: 'io.spring.javaformat'
 apply plugin: 'io.spring.security.release'
 apply plugin: 's101'
 
+node {
+    version = "24.15.0"
+}
+
 group = "org.springframework.ldap"
 description = "Spring LDAP"