Editorial: Oxford comma needed

[jenstrickland]

Referring to https://www.w3.org/TR/2025/PR-dpub-aria-1.1-20250318/

Current

This specification defines a module of WAI-ARIA for digital publishing, including roles, states, properties and values. It impacts several audiences:

Suggested

This specification defines a module of WAI-ARIA for digital publishing, including roles, states, properties, and values. It impacts several audiences:

[daniel-montalvo]

Thanks @jenstrickland fixed