fix: remove mock export (#4369)

## Explanation

This pr removes a mock export.

## References

## Changelog

None

## Checklist

- [ ] I've updated the test suite for new or updated code as appropriate
- [ ] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [ ] I've highlighted breaking changes using the "BREAKING" category
above as appropriate

packages/accounts-controller/src/index.ts

@@ -17,4 +17,3 @@ export type {
 } from './AccountsController';
 export { AccountsController } from './AccountsController';
 export { keyringTypeToName, getUUIDFromAddressOfNormalAccount } from './utils';
-export { createMockInternalAccount } from './tests/mocks';