Drop old int4 PK column for events

- Drop column `id_convert_to_bigint`

Column was ignored with
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/69337.

https://gitlab.com/gitlab-org/gitlab/-/issues/338072

Changelog: other

db/post_migrate/20210922082019_drop_int4_column_for_events.rb

+# frozen_string_literal: true
+
+class DropInt4ColumnForEvents < Gitlab::Database::Migration[1.0]
+  enable_lock_retries!
+
+  def change
+    remove_column :events, :id_convert_to_bigint, :integer, null: false, default: 0
+  end
+end

db/schema_migrations/20210922082019

+011b714ee5d4389a5a172ae687eea3a814915fb39a5e5eae38b6ee423a903eaf
\ No newline at end of file

db/structure.sql

@@ -13734,7 +13734,6 @@ CREATE SEQUENCE error_tracking_errors_id_seq
 ALTER SEQUENCE error_tracking_errors_id_seq OWNED BY error_tracking_errors.id;
 
 CREATE TABLE events (
-    id_convert_to_bigint integer DEFAULT 0 NOT NULL,
     project_id integer,
     author_id integer NOT NULL,
     target_id integer,

spec/migrations/20210922082019_drop_int4_column_for_events_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require_migration!('drop_int4_column_for_events')
+
+RSpec.describe DropInt4ColumnForEvents do
+  let(:events) { table(:events) }
+
+  it 'correctly migrates up and down' do
+    reversible_migration do |migration|
+      migration.before -> {
+        expect(events.column_names).to include('id_convert_to_bigint')
+      }
+
+      migration.after -> {
+        events.reset_column_information
+        expect(events.column_names).not_to include('id_convert_to_bigint')
+      }
+    end
+  end
+end