[dashboard] dashboard references lost when dashboard updated from listing page

[nreese]

Regression caused by #240182.

DashboardStorage.update has an existing bug where calling update without references will save dashboard without references. #240182 caused this existing bug to be accessible via the UI. The highlighted changes updateDashboardMeta cause DashboardStorage.update to be called without references. This causes saved object to be stored with empty reference array.

steps

• install sample web logs
• create new dashboard, add by reference len panel
• saved dashboard
• got to listing page
• click "View details" action for dashboard
• edit description and "Update dashboard"
• Open dashboard. Notice how lens panel is now broken.
• View dashboard saved object. References array is empty.

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)