Remove redundant pipeline loggers

What does this MR do and why?

These logs have negligible time periods:

• config_external_merge: https://log.gprd.gitlab.net/goto/0b76c150-5c4e-11ed-b0ec-930003e0679c
• config_external_verify: https://log.gprd.gitlab.net/goto/26030510-5c4e-11ed-8d37-e9a2f393ea2a
• config_mapper_normalize: https://log.gprd.gitlab.net/goto/59086400-5c4e-11ed-b0ec-930003e0679c
• pipeline_seed_merge_variables: https://log.gprd.gitlab.net/goto/e14874e0-5c4e-11ed-b0ec-930003e0679c

And this MR removes them to reduce the log size/confusion.

As a next step, I'd like to remove these too;

• pipeline_step_gitlab_ci_pipeline_chain_assign_partition: https://log.gprd.gitlab.net/goto/19df4db0-5c4f-11ed-b0ec-930003e0679c
• pipeline_step_gitlab_ci_pipeline_chain_create_cross_database_associations: https://log.gprd.gitlab.net/goto/e9ed1ad0-5c51-11ed-8d37-e9a2f393ea2a
• pipeline_step_gitlab_ci_pipeline_chain_limit_activity: https://log.gprd.gitlab.net/goto/38462c30-5c52-11ed-8d37-e9a2f393ea2a
• pipeline_step_gitlab_ci_pipeline_chain_metrics: https://log.gprd.gitlab.net/goto/672e3ab0-5c52-11ed-b0ec-930003e0679c
• pipeline_step_gitlab_ci_pipeline_chain_remove_unwanted_chat_jobs: https://log.gprd.gitlab.net/goto/803dc980-5c52-11ed-8d37-e9a2f393ea2a
• pipeline_step_gitlab_ci_pipeline_chain_stop_dry_run: https://log.gprd.gitlab.net/goto/a41b4e40-5c52-11ed-8d37-e9a2f393ea2a

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.