[lib] Don't show Farcaster prompt for users after they unlink Farcaster

Summary: If the user unlinks their Farcaster identity, we should set it to `NO_FID_METADATA` so they don't get prompted again.

Test Plan: I looked through the code for places that call `useCurrentUserFID` to see where `undefined`/`null` is differentiated. I saw that `ConnectFarcasterAlertHandler` calls `shouldSkipConnectFarcasterAlert`, which differentiates the two. I confirmed that setting `NO_FID_METADATA` is better, so that we return `null` and so that `ConnectFarcasterAlertHandler` doesn't prompt the user to connect their Farcaster account in this case

Reviewers: will

Reviewed By: will

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13735

lib/utils/farcaster-utils.js

@@ -3,10 +3,7 @@
 import invariant from 'invariant';
 import * as React from 'react';
 
-import {
-  setSyncedMetadataEntryActionType,
-  clearSyncedMetadataEntryActionType,
-} from '../actions/synced-metadata-actions.js';
+import { setSyncedMetadataEntryActionType } from '../actions/synced-metadata-actions.js';
 import { IdentityClientContext } from '../shared/identity-client-context.js';
 import { syncedMetadataNames } from '../types/synced-metadata-types.js';
 import { useSelector, useDispatch } from '../utils/redux-utils.js';
@@ -71,9 +68,10 @@ function useUnlinkFID(): () => Promise<void> {
     await unlinkFarcasterAccount();
 
     dispatch({
-      type: clearSyncedMetadataEntryActionType,
+      type: setSyncedMetadataEntryActionType,
       payload: {
         name: syncedMetadataNames.CURRENT_USER_FID,
+        data: NO_FID_METADATA,
       },
     });
   }, [dispatch, unlinkFarcasterAccount]);