Add Preview callout to Glue Jobs Monitoring docs page (#37679)

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: warrierr

content/en/data_observability/jobs_monitoring/glue.md

@@ -10,6 +10,8 @@ further_reading:
     text: 'AWS Integration'
 ---
 
+<div class="alert alert-info">Jobs Monitoring for AWS Glue is in Preview.</div>
+
 ## Overview
 
 [Data Observability: Jobs Monitoring][6] gives visibility into the performance and reliability of your AWS Glue jobs.