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.

Closes gh-2336

Signed-off-by: Joe Grandja <10884212+jgrandja@users.noreply.github.com>

Author: jgrandja

docs/spring-authorization-server-docs.gradle

@@ -16,6 +16,10 @@ compileJava {
 	options.compilerArgs << '-parameters'
 }
 
+node {
+    version = "24.15.0"
+}
+
 antora {
 	options = [clean: true, fetch: !project.gradle.startParameter.offline, stacktrace: true]
 	environment = [