Preface docs page out of date and has missing links

[rodburns]

Version

NA

What behaviour are you expecting?

NA

What actual behaviour are you seeing?

The preface page has missing links in the list. The ComputeCpp references should be removed since it has been deprecated. Could add links to DPC++ to replace these.

What steps are required to reproduce the bug?

NA

Minimal test case

NA

Anything else we should know?

NA