Fix deployment chat notifications for tags

What does this MR do and why?

This fixes a bug that causes deployment chat notifications to not be sent when a tag is deployed. The problem was introduced in !74423 (merged) and was noticed by the author of that MR @svengt. This MR simply implements their proposed solution to the problem, because I could not find an issue or MR for their fix yet.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Create a pipeline including a deployment job
   • Launch a Gitpod on this branch
   • Follow the instructions to enable pipeline runners on Gitpod
   • Create a project on your Gitpod instance
   • Create a static environment on your project and add the deploy stage to your .gitlab-ci.yml
2. Configure a chat notification service for the repository, e.g., Slack
3. Configure this notification service to only send notifications for Default branch and protected branches
4. Create a tag for a commit
5. Run the deployment pipeline for said tag, you should receive a deployment notification

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.