Remove unused `BuildProcessWorker`

What does this MR do?

Remove BuildProcessWorker as this is no longer needed. We can remove it as this worker is just introduced, so we not gonna break any of the installs. We migrated all the logic to PipelineProcessWorker. It was introduced during %12.2 cycle so, no new installations should be using, so there's no need to perform data migration.

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Merge request performance guidelines
• Style guides

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/65539

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/65457