ci: remove unnecessary docker services and variables

Eliminate unused Docker host variables and services from the CI 
configuration. This simplifies the build process and reduces 
potential complexities in the CI pipeline.

.gitlab-ci.yml

@@ -6,15 +6,10 @@ include:
 stages:
 - build
 
-variables:
-  DOCKER_HOST: tcp://docker:2375/
-
 image: buildtool/build-tools:${BUILDTOOLS_VERSION}
 
 build:
   stage: build
-  services:
-  - docker:${DOCKER_DIND_VERSION}
   script:
   - unset BUILDTOOLS_CONTENT
   - build