perf(dashboard): dashboard list endpoint returning large and unnecessary data (#29121)

Co-authored-by: Michael S. Molina <michael.s.molina@gmail.com>
Co-authored-by: Michael S. Molina <70410625+michael-s-molina@users.noreply.github.com>

UPDATING.md

@@ -34,6 +34,7 @@ assists people when migrating to a new version.
 - [31173](https://github.com/apache/superset/pull/31173) Modified `fetch_csrf_token` to align with HTTP standards, particularly regarding how cookies are handled. If you encounter any issues related to CSRF functionality, please report them as a new issue and reference this PR for context.
 - [31385](https://github.com/apache/superset/pull/31385) Significant docker refactor, reducing access levels for the `superset` user, streamlining layer building, ...
 - [31503](https://github.com/apache/superset/pull/31503) Deprecating python 3.9.x support, 3.11 is  now the recommended version and 3.10 is still supported over the Superset 5.0 lifecycle.
+- [29121](https://github.com/apache/superset/pull/29121) Removed the `css`, `position_json`, and `json_metadata` from the payload of the dashboard list endpoint (`GET api/v1/dashboard`) for performance reasons.
 
 ### Potential Downtime
 

superset/dashboards/api.py

@@ -193,9 +193,6 @@ class DashboardRestApi(BaseSupersetModelRestApi):
         "status",
         "slug",
         "url",
-        "css",
-        "position_json",
-        "json_metadata",
         "thumbnail_url",
         "certified_by",
         "certification_details",