default N-panel open for animation editors

The Graph, Driver, and Dopesheet's (and sub modes) properties panel
(N-Panel) are now open by default. This includes the editors in the
default Animation workspace.

Note that, because the Timeline is implemented as a special mode of the
Dopesheet, switching between Timeline and Dopesheet will *not* change
the visibility of the properties panel.

Maniphest Tasks: T97980

Differential Revision: https://developer.blender.org/D14910

source/blender/editors/space_graph/space_graph.c

@@ -90,7 +90,6 @@ static SpaceLink *graph_create(const ScrArea *UNUSED(area), const Scene *scene)
   BLI_addtail(&sipo->regionbase, region);
   region->regiontype = RGN_TYPE_UI;
   region->alignment = RGN_ALIGN_RIGHT;
-  region->flag = RGN_FLAG_HIDDEN;
 
   /* main region */
   region = MEM_callocN(sizeof(ARegion), "main region for graphedit");