git-artifacts: fix bundle-artifacts' file names for out-of-band releases

[dscho]

When releasing Git for Windows v2.41.0(2), an out-of-band release, the bundle-artifacts contained announcement-<ver> and release-notes-<ver> files using the parenthesized form of the version instead of the dotted one ("2.41.0(2)" instead of "2.41.0.2").

This was unintentional, and while I implemented a workaround, the git-artifacts workflow should be fixed to produce the expected file names.