docs: Fix typo in useMutation.md (#8397)

Fix typo in useMutation.md

Author: centraldogma99

docs/framework/react/reference/useMutation.md

@@ -59,7 +59,7 @@ mutate(variables, {
 - `mutationKey: unknown[]`
   - Optional
   - A mutation key can be set to inherit defaults set with `queryClient.setMutationDefaults`.
-- `networkMode: 'online' | 'always' | 'offlineFirst`
+- `networkMode: 'online' | 'always' | 'offlineFirst'`
   - Optional
   - defaults to `'online'`
   - see [Network Mode](../../guides/network-mode) for more information.