chore: Disable account syncing in prod (#27943)

## **Description**

This PR disables account syncing in prod until we have e2e tests and
documentation of proper testing

[![Open in GitHub
Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/MetaMask/metamask-extension/pull/27943?quickstart=1)

## **Related issues**

Fixes:

## **Manual testing steps**

1. `yarn build`
2. Account syncing should not occur

## **Screenshots/Recordings**

<!-- If applicable, add screenshots and/or recordings to visualize the
before and after of your change. -->

### **Before**

<!-- [screenshots/recordings] -->

### **After**

<!-- [screenshots/recordings] -->

## **Pre-merge author checklist**

- [ ] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/CODING_GUIDELINES.md).
- [ ] I've completed the PR template to the best of my ability
- [ ] I’ve included tests if applicable
- [ ] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [ ] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

---------

Co-authored-by: Mark Stacey <markjstacey@gmail.com>

app/scripts/metamask-controller.js

@@ -155,6 +155,7 @@ import {
   NotificationServicesPushController,
   NotificationServicesController,
 } from '@metamask/notification-services-controller';
+import { isProduction } from '../../shared/modules/environment';
 import { methodsRequiringNetworkSwitch } from '../../shared/constants/methods-tags';
 
 ///: BEGIN:ONLY_INCLUDE_IF(build-mmi)
@@ -1531,7 +1532,7 @@ export default class MetamaskController extends EventEmitter {
         },
       },
       env: {
-        isAccountSyncingEnabled: isManifestV3,
+        isAccountSyncingEnabled: !isProduction() && isManifestV3,
       },
       messenger: this.controllerMessenger.getRestricted({
         name: 'UserStorageController',