[icudotnet] Run Windows jobs on dallas-windows-slave-2
[icudotnet] Run Windows jobs on dallas-windows-slave-2

Run Windows jobs on `dallas-windows-slave-2` because the others
currently give problems.

Change-Id: Iaf820c80503fd680b1a2566eb3f5318403ea4179

sillsdev/ci-builder-scripts,sillsdev/ci-builder-scripts,sillsdev/ci-builder-scripts