fix: correct flushFileReader helper to avoid infinite recursion

Co-authored-by: hyoban <38493346+hyoban@users.noreply.github.com>

web/app/components/rag-pipeline/components/update-dsl-modal.spec.tsx

@@ -153,7 +153,7 @@ describe('UpdateDSLModal', () => {
 
   // Helper function to flush FileReader microtasks
   const flushFileReader = async () => {
-    await flushFileReader()
+    await new Promise<void>(resolve => queueMicrotask(resolve))
   }
 
   beforeEach(() => {