[BUG] default columns being re-added after being removed on saved searches

[rossmmurray]

Description

When removing a default column from a saved search, the default column is re-added once the saved search is reloaded.

To Reproduce

1. Ensure you have default columns set (advanced settings --> default columns) e.g. source
2. Go to discover and run some query.
3. remove a default column e.g. source
4. Click Save (top right)
5. Reload the page
6. The source column will be re-added

Expected behavior

I'd expect the default column not to be re-added when reloading the page.

OpenSearch Version
2.17

Dashboards Version
2.17

Host/Environment (please complete the following information):

• OS: macOS
• Chrome 131.0.6778.205