Drop the unreachable 404 from save_dashboard

write_draft creates a first draft for a name that does not exist yet, so
it raises only StaleVersion — the DashboardNotFound arm never ran.

backend/fluksio/api/routes/dashboards.py

@@ -125,8 +125,6 @@ async def save_dashboard(
         raise HTTPException(status_code=422, detail="The name in the body must match")
     try:
         saved = await run_in_threadpool(store.write_draft, body, body.version)
-    except DashboardNotFound:
-        raise HTTPException(status_code=404, detail=f"No dashboard named '{name}'")
     except StaleVersion as exc:
         raise HTTPException(
             status_code=409,