#47404: ci: fix up branch CI audit workflow
Description of Change
Don't send the Slack message on the workflow itself failing (we've seen it happen due to 5XX errors from GitHub servers or general GHA issues), ignores failures of the workflow itself, fixes some syntax errors which slipped in, and updates the Slack message to only send when run on main so we can more easily test this on branches without spamming ourselves
Checklist
- PR description included and stakeholders cc'd
Release Notes
Notes: none
Backports
No Backports Requested
This pull request doesn't have any backports requested or created for older release branches.
What are backports?
Backports are copies of changes made to the main branch that are applied to older release branches. They ensure that bug fixes and important changes are available in maintained older versions of Electron.
Semver Impact
Semantic Versioning helps users understand the impact of updates:
- Major (X.y.z): Breaking changes that may require code modifications
- Minor (x.Y.z): New features that maintain backward compatibility
- Patch (x.y.Z): Bug fixes that don't change the API
- None: Changes that don't affect using facing parts of Electron