Update Marketplace docs to reflect README.md

[peter-lyons-kehl]

Thank you for CodeTour.

https://marketplace.visualstudio.com/items?itemName=vsls-contrib.codetour is mostly identical to https://github.com/microsoft/codetour/blob/main/README.md, except that

• https://github.com/microsoft/codetour/blob/main/README.md#versioning-tours reads: "None - The tour isn't associated with any ref. The benefit...", but
• https://marketplace.visualstudio.com/items?itemName=vsls-contrib.codetour has extra text - and that doesn't seem to apply. The extra text is here in bold: "None - The tour isn't associated with any ref. When you select this option, tour steps will be associated with code via a regex pattern, as opposed to a line number. This ensures that they can retain resilient if the attached line is moved around the file. The benefit..."

I believe the Marketplace text is obsolete, because when I do record with "None" as git ref, it does NOT change to recording pattern, but it still records line. Please re-consider this behavior (and create an issue for it, if it doesn't work as intended).

FYI: https://open-vsx.org/extension/vsls-contrib/codetour has the above difference fixed.