feat: remove noisy labels from slack alert msg

Remove a list of labels that aren't useful during incident response and only useful for analytics purposes.

Before	After

1. Going with an allow list
   • Only allowing a certain amount of labels to show. This can be tedious and error-prone because the engineer creating the alert might not know that there is an allow list and that label will not be shown (assuming it will)
2. Gowing with a disallow list
   • Explicitly remove "junk" labels that we don't care about, this can lead to more maintenance work but can be less surprising to authors of the alert if they add their label and it doesn't show up.

Reference: gitlab-com/gl-infra/reliability#15894