Merge branch 'chore/remove_old_variables' into 'master'

Cleanout leftover variables from buildx refactoring

See merge request https://gitlab.com/gitlab-org/terraform-images/-/merge_requests/234



Merged-by: Timo Furrer <tfurrer@gitlab.com>
Approved-by: Timo Furrer <tfurrer@gitlab.com>
Co-authored-by: Birger J. Nordølum <contact@mindtooth.no>

.gitlab-ci.yml

@@ -13,8 +13,6 @@ include:
 variables:
   BASE_IMAGE: "alpine:3.18.4"
   BUILD_IMAGE_NAME: "$CI_REGISTRY_IMAGE/branches/$CI_COMMIT_REF_SLUG-$TERRAFORM_VERSION:$CI_COMMIT_SHA"
-  BUILDX_VERSION: "0.11.2"
-  DOCKER_BUILDKIT: "1"
   DOCKER_DIND_IMAGE: "docker:24.0.6-dind"
   NODE_IMAGE: "node:lts-slim"
   PLATFORMS: linux/amd64,linux/arm64