CQ-4358664: adjust documentation on local UI test execution

[nortoneo]

CQ-4358664 selenium image update

Description

Related Issue

CQ-4358664

Motivation and Context

use multi-arch selenium docker images for local ui tests

How Has This Been Tested?

Executed ui tests locally against AEM sandbox WKND instance.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.