Add a proper deprecation comment to GlobalDevServicesConfig.Enabled

Per https://quarkusio.zulipchat.com/#narrow/channel/187030-users/topic/.60GlobalDevServicesConfig.2EEnabled.2Eclass.60.20deprecated.3F

(cherry picked from commit 7288045)

Author: gsmet

core/deployment/src/main/java/io/quarkus/deployment/dev/devservices/GlobalDevServicesConfig.java

@@ -34,6 +34,10 @@ public class GlobalDevServicesConfig {
     @ConfigItem(generateDocumentation = false)
     public Optional<Duration> timeout;
 
+    /**
+     * @deprecated Please, use {@link DevServicesConfig.Enabled} instead.
+     */
+    @Deprecated(forRemoval = true, since = "3.18")
     public static class Enabled implements BooleanSupplier {
 
         final GlobalDevServicesConfig config;