Update addinsnote.md

Update note to direct to Docs.com. Removed other link, I don't think there's a corresponding page to this anymore, but the overview should be enough to guide folks.

Author: mikewaretena

docs/includes/addinsnote.md

@@ -1,2 +1,2 @@
 > [!NOTE]
-> Interested in developing solutions that extend the Office experience across [multiple platforms](https://dev.office.com/add-in-availability)? Check out the new [Office Add-ins model](https://dev.office.com/docs/add-ins/overview/office-add-ins). Office Add-ins have a small footprint compared to VSTO Add-ins and solutions, and you can build them by using almost any web programming technology, such as HTML5, JavaScript, CSS3, and XML.
+> Interested in developing solutions that extend the Office experience across multiple platforms? Check out the new [Office Add-ins model](https://docs.microsoft.com/en-us/office/dev/add-ins/overview/office-add-ins). Office Add-ins have a small footprint compared to VSTO Add-ins and solutions, and you can build them by using almost any web programming technology, such as HTML5, JavaScript, CSS3, and XML.