Ensure the correct migration for index creation

The following methods must be called in post-migrations:

• remove_concurrent_index :example, :example_id, unique: false, name: INDEX_NAME
• remove_concurrent_index :example, :example_id, name: INDEX_NAME

If one of these methods is used in a regular migration. The rubocop job should fail.

The following methods must be called in regular migrations:

• remove_concurrent_index :example, :example_id, unique: true, name: UNIQUE_INDEX_NAME

If one of these methods is used in a post-migration. The rubocop job should fail.