Drop old int4 PK columns for ci_job_artifacts

- Drop column `id_convert_to_bigint`
- Drop column `job_id_convert_to_bigint`

Columns were ignored in 14.3 with
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68770.

https://gitlab.com/gitlab-org/gitlab/-/issues/338068.

Changelog: other

db/post_migrate/20210922021816_drop_int4_columns_for_ci_job_artifacts.rb

+# frozen_string_literal: true
+
+class DropInt4ColumnsForCiJobArtifacts < Gitlab::Database::Migration[1.0]
+  enable_lock_retries!
+
+  def change
+    remove_column :ci_job_artifacts, :id_convert_to_bigint, :integer, null: false, default: 0
+    remove_column :ci_job_artifacts, :job_id_convert_to_bigint, :integer, null: false, default: 0
+  end
+end

db/schema_migrations/20210922021816

+1d18e061cb5bcdaa7d3fcea93e58d65a6f2c8b557fe53ba461b6cfa570f565be
\ No newline at end of file

db/structure.sql

@@ -11535,9 +11535,7 @@ CREATE SEQUENCE ci_instance_variables_id_seq
 ALTER SEQUENCE ci_instance_variables_id_seq OWNED BY ci_instance_variables.id;
 
 CREATE TABLE ci_job_artifacts (
-    id_convert_to_bigint integer DEFAULT 0 NOT NULL,
     project_id integer NOT NULL,
-    job_id_convert_to_bigint integer DEFAULT 0 NOT NULL,
     file_type integer NOT NULL,
     size bigint,
     created_at timestamp with time zone NOT NULL,

spec/migrations/20210922021816_drop_int4_columns_for_ci_job_artifacts_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require_migration!('drop_int4_columns_for_ci_job_artifacts')
+
+RSpec.describe DropInt4ColumnsForCiJobArtifacts do
+  let(:ci_job_artifacts) { table(:ci_job_artifacts) }
+
+  it 'correctly migrates up and down' do
+    reversible_migration do |migration|
+      migration.before -> {
+        expect(ci_job_artifacts.column_names).to include('id_convert_to_bigint')
+        expect(ci_job_artifacts.column_names).to include('job_id_convert_to_bigint')
+      }
+
+      migration.after -> {
+        ci_job_artifacts.reset_column_information
+        expect(ci_job_artifacts.column_names).not_to include('id_convert_to_bigint')
+        expect(ci_job_artifacts.column_names).not_to include('job_id_convert_to_bigint')
+      }
+    end
+  end
+end