ci: clean up GitLab CI configuration

Removes unused Docker variables from the CI configuration to simplify 
the setup. This change streamlines the build process by eliminating 
redundant settings that are not required for the current build 
pipeline.

.gitlab-ci.yml

@@ -5,16 +5,7 @@ stages:
 - build
 - deploy-prod
 
-variables:
-  DOCKER_HOST: tcp://docker:2376
-  DOCKER_TLS_CERTDIR: "/certs"
-  DOCKER_TLS_VERIFY: 1
-  DOCKER_CERT_PATH: "$DOCKER_TLS_CERTDIR/client"
-  DOCKER_DRIVER: overlay2
-
 image: buildtool/build-tools:${BUILDTOOLS_VERSION}
-services:
-- docker:${DOCKER_DIND_VERSION}
 
 build:
   stage: build