Resolve "CI/CD jobs: Wrong value in env. variable CI_DEPLOY_USER using <gitlab-deploy-token> deploy token"

What does this MR do?

Fixes deploy_tokens_variables on Ci::Build. It was using DeployToken#name instead of DeployToken#username

On master

 {:key=>"CI_DEPLOY_USER", :value=>"gitlab-deploy-token", :public=>true},
 {:key=>"CI_DEPLOY_PASSWORD", :value=>"123456789", :public=>false},

On this branch

 {:key=>"CI_DEPLOY_USER", :value=>"gitlab+deploy-token-14", :public=>true},
 {:key=>"CI_DEPLOY_PASSWORD", :value=>"123456789", :public=>false},

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a Backend maintainer
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #46454 (closed)