Add Terraform GitLab Provider to Engineering projects

Why is this change being made?

This MR adds "Terraform GitLab Project" (currently hosted on GitHub.com) to https://about.gitlab.com/handbook/engineering/projects/ as it's managed by devopsconfigure.

https://gitlab-terraform-provider.about.gitlab-review.app/handbook/engineering/projects/#terraform-provider-gitlab	https://gitlab-terraform-provider.about.gitlab-review.app/handbook/engineering/development/ops/configure/#gitlab-terraform-provider

Author Checklist

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• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
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