As it turns out, you cannot use `<uap17:UpdateWhileInUse>`
(or any other newer namespace) unless you declare a corresponding
`MaxVersionTested` in your package manifest.
It does not appear that there's a reason for this, it just is.
`MaxVersionTested` is not to be confused with the `maxversiontested`,
which is something else entirely, but I updated it for safe measure.
Since `maxversiontested` is not a "max", but rather a list
of tested versions, it gets appended to the end of the list.
Closes#18119
32eeefd89e