Jumoo.Json: tagged the live NuGet releases

Repo: Jumoo/Jumoo.Json

Jumoo.Json: dropped the planned 17.0.3 / 18.0.4 releases. Nothing in the library has changed since the versions on NuGet, only CI, build props and package metadata
Tagged the untagged July releases at the commits recorded in their nuspecs: release/17.0.2 (8af3dbd, NuGet) and release/18.0.3 (64d91c0, NuGet)
Kept the release/ prefix so the tags don't trigger the new v* release workflow
Closed the release issue and ticked Jumoo.Json off the release worklist