ci: remove unused docker configuration from CI files

Removes unnecessary Docker host variables and service settings from 
`.gitlab-ci.yml` to simplify the CI/CD pipeline configuration. This 
streamlines the build process by focusing on the essential tasks 
and reduces potential configuration errors.

.gitlab-ci.yml

@@ -5,15 +5,10 @@ stages:
 - build
 - deploy-prod
 
-variables:
-  DOCKER_HOST: tcp://docker:2375/
-
 image: buildtool/build-tools:${BUILDTOOLS_VERSION}
 
 build:
   stage: build
-  services:
-  - docker:${DOCKER_DIND_VERSION}
   script:
   - build
   - curl -Os https://uploader.codecov.io/latest/linux/codecov