improve logic of 3d scene size (#7619)

## Summary

improve 3d scene size logic, for preview3d, it should not have target
size

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7619-improve-logic-of-3d-scene-size-2cd6d73d36508101b9f5dcef9bbe1314)
by [Unito](https://www.unito.io)

tests-ui/tests/composables/useLoad3dViewer.test.ts

@@ -164,7 +164,7 @@ describe('useLoad3dViewer', () => {
         width: undefined,
         height: undefined,
         getDimensions: undefined,
-        isViewerMode: true
+        isViewerMode: false
       })
 
       expect(mockLoad3dService.copyLoad3dState).toHaveBeenCalledWith(