ICU-22977 Temp fix for MSVC builds: SkipUWP

[mihnita]

Checklist

• Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22977
• Required: The PR title must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
• Required: Each commit message must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• Issue accepted (done by Technical Committee after discussion)
• Tests included, if applicable
• API docs and/or User Guide docs changed or added, if applicable

[mihnita]

Temporary solution to get a green CI.

To check if we still want to support UWP:

"If you are starting to develop Windows apps, we recommend you consider using the Windows App SDK, and WinUI rather than UWP. Although still supported, UWP is not under active development."

https://learn.microsoft.com/en-us/windows/uwp/get-started/universal-application-platform-guide

If we drop support for UWP then we should also remove the icu4c/source/.../*_uwp.vcxproj files, remove ../allinone/Build.Windows.UWP.ProjectConfiguration.props and update ./docs/userguide/icu4c/build.md