Remove partial index for Hashed Storage migration

This is a cleanup issue for when we remove Legacy Storage support completely.
In https://gitlab.com/gitlab-org/gitlab/-/issues/194066 we added a
temporary partial index to make it possible
to run the migration on the biggest instances without taking too long or be impractical.

Changelog: other

db/migrate/20210601132134_remove_partial_index_for_hashed_storage_migration.rb

+# frozen_string_literal: true
+
+class RemovePartialIndexForHashedStorageMigration < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  def up
+    remove_concurrent_index :projects, :id, name: 'index_on_id_partial_with_legacy_storage'
+  end
+
+  def down
+    add_concurrent_index :projects, :id, where: 'storage_version < 2 or storage_version IS NULL', name: 'index_on_id_partial_with_legacy_storage'
+  end
+end

db/schema_migrations/20210601132134

+966299fecd160b594f0837f19cc01b38fc365fa749982f9245c296d912e3eb2f
\ No newline at end of file

db/structure.sql

@@ -23847,8 +23847,6 @@ CREATE INDEX index_oauth_openid_requests_on_access_grant_id ON oauth_openid_requ
 
 CREATE UNIQUE INDEX index_on_deploy_keys_id_and_type_and_public ON keys USING btree (id, type) WHERE (public = true);
 
-CREATE INDEX index_on_id_partial_with_legacy_storage ON projects USING btree (id) WHERE ((storage_version < 2) OR (storage_version IS NULL));
-
 CREATE INDEX index_on_identities_lower_extern_uid_and_provider ON identities USING btree (lower((extern_uid)::text), provider);
 
 CREATE UNIQUE INDEX index_on_instance_statistics_recorded_at_and_identifier ON analytics_instance_statistics_measurements USING btree (identifier, recorded_at);