tweak packit config to reduce to 3 days

@jlebon pointed out that we have a semantic conflict between our new weekly release cadence and packit for Fedora defaulting to 7 days of karma - the updates keep obsoleting.

Let's reduce our packit config for Fedora to 3 days - and keep improving our CI so we can reliably release fast enough.

Search the repository for the Packit configuration and identify the Fedora karma setting. Change the default from 7 days to 3, then run the repository's relevant configuration or CI checks to confirm the setting is valid and the release automation still passes.

Written by the indexing model from the issue text.