Uncomment and fix "Notify if Job Fails"

[xgreenx]

CI failed to notify the slack channel, we commented it for now.

We need to fix the notification and enable it again

[cpp-phoenix]

Hey @xgreenx, I have experience working with slack and discord notifications. I can work on it

[xgreenx]

You are welcome, but I'm not sure how you plan to check that action actually works, because it requires token that you don't have access too