Original install method (e.g. download page, yum, from source, etc.): Serverless production

Description of the problem including expected versus actual behavior:

The index size feature (app/synthetics/settings/data-retention) appears broken in serverless Synthetics. Tested with admin, editor, and viewer roles.

Here you can see the index size is displayed as 0 bytes. However, at least two of these indices should have data in them as evidenced from my available monitors.

https://www.loom.com/share/484ac62a86fa47bebd9ae0667f82d28e?sid=daebe9d3-9bc5-4254-b75d-e68fb54b058d

Steps to reproduce:

1. Create an observability project
2. Create a synthetics monitor and wait for data
3. Navigate to app/synthetics/settings/data-retention. Observe that the index size is displayed at 0 bytes