Replace deprecated SelectLegacy with Select in AccountIntegrationsPage

Description

There is an ongoing TODO pattern in the codebase to migrate deprecated
SelectLegacy components to the modern Select component from
@rocket.chat/fuselage.

The AccountIntegrationsPage.tsx currently still uses SelectLegacy and should
be updated to use Select.

Affected file

• apps/meteor/client/views/account/integrations/AccountIntegrationsPage.tsx

Current code

SelectLegacy is imported and used in the form controller:

import { SelectLegacy, ... } from '@rocket.chat/fuselage';

render={({ field }) => (
  <SelectLegacy
    {...field}
    options={options}
    placeholder={t('Select_an_option')}
  />
);

Problem

• SelectLegacy is deprecated and should no longer be used.
• This usage does not require advanced features such as renderItem or
  renderSelected.
• Similar simple cases have already been migrated across the codebase.

Examples of already-migrated components include:

• RoleForm.tsx
• QueueListFilter.tsx
• ConditionForm.tsx

Proposed solution

Replace SelectLegacy with the modern Select component.

Example:

import { Select, ... } from '@rocket.chat/fuselage';

render={({ field }) => (
  <Select
    {...field}
    options={options}
    placeholder={t('Select_an_option')}
  />
);

This aligns the component with current standards and removes deprecated usage.

Verification

• No visual changes expected.
• No functional behavior changes expected.
• Component props remain the same.
• Follows an existing migration pattern already used in 8+ files in the
  codebase.

Open apps/meteor/client/views/account/integrations/AccountIntegrationsPage.tsx and compare its simple SelectLegacy usage with the migrated patterns in RoleForm.tsx, QueueListFilter.tsx, and ConditionForm.tsx. Replace the deprecated component while preserving the existing options, placeholder, and field props, then verify that no visual or functional changes are introduced.