refactor: create shared react-i18next mock to reduce duplication (#29711)

web/app/components/datasets/external-knowledge-base/create/index.spec.tsx

@@ -15,13 +15,6 @@ jest.mock('next/navigation', () => ({
   }),
 }))
 
-// Mock react-i18next
-jest.mock('react-i18next', () => ({
-  useTranslation: () => ({
-    t: (key: string) => key,
-  }),
-}))
-
 // Mock useDocLink hook
 jest.mock('@/context/i18n', () => ({
   useDocLink: () => (path?: string) => `https://docs.dify.ai/en${path || ''}`,