Remove workflow for automatically adding issues to the zarf project (#…

…2239)

## Description
Remove the workflow that would automatically add an issue to the [Zarf
Project Board](https://github.com/orgs/defenseunicorns/projects/1). This
operation is now handled in a workflow at the project level.

This reduces the overall permissions footprint of the Zarf workflows.


## Related Issue
Fixes #2238