release.yml: keep previews and an older line's tag off GitHub's Latest #44

With two lines (#40, CONTRIBUTING.md "Branches and releases"), a v10.x tag pushed after v11.0.0 exists must not become the repository's Latest release, and a v11.0.0-preview.N tag must be published as a prerelease that is not Latest either. release.yml today passes --prerelease for a version with a - suffix and otherwise lets GitHub decide.

Port what CodoMetis.ValueRanges merged in its PR #156 (release.yml, "Create the release"): --prerelease --latest=false for a prerelease, and --latest=false for a stable tag when the current Latest release is newer by sort -V. Add the assertion to ReleaseWiringConventionTests, reading the script lines, and seed it (flags removed, older-line guard removed) to show it fails.

Done when a 10.x tag after 11.0.0, and any preview, leaves Latest where it is.