fix (Cherrypick v12.7.0 ): disable account syncing (#28361)

## **Description**

Cherrypick of #28359
(afa7365)

This disables account syncing in v12.7.0

[![Open in GitHub
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## **Related issues**

Fixes:

## **Manual testing steps**

1. Go to this page...
2.
3.

## **Screenshots/Recordings**

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before and after of your change. -->

### **Before**

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### **After**

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## **Pre-merge author checklist**

- [x] 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).
- [x] I've completed the PR template to the best of my ability
- [x] I’ve included tests if applicable
- [x] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] 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: Mathieu Artu <[email protected]>

app/scripts/metamask-controller.js

@@ -156,6 +156,7 @@ import {
   NotificationServicesPushController,
   NotificationServicesController,
 } from '@metamask/notification-services-controller';
+import { isProduction } from '../../shared/modules/environment';
 import {
   methodsRequiringNetworkSwitch,
   methodsThatCanSwitchNetworkWithoutApproval,
@@ -1568,7 +1569,7 @@ export default class MetamaskController extends EventEmitter {
         },
       },
       env: {
-        isAccountSyncingEnabled: isManifestV3,
+        isAccountSyncingEnabled: !isProduction() && isManifestV3,
       },
       messenger: this.controllerMessenger.getRestricted({
         name: 'UserStorageController',