chore: decrease ui observability to warn (#9658)

These errors are not acted upon and is not something we can act on.
Reducing it's level to WARN following
https://github.com/Unleash/unleash/blob/main/website/docs/contributing/ADRs/overarching/logging-levels.md

src/lib/features/ui-observability-controller/ui-observability-controller.ts

@@ -47,7 +47,7 @@ export class UiObservabilityController extends Controller {
     }
 
     async recordUiError(req: Request, res: Response): Promise<void> {
-        this.logger.error(
+        this.logger.warn(
             `UI Observability Error: ${req.body.errorMessage}`,
             req.body.errorStack,
         );