Merge branch 'sarnold-add-back-index-structure-sql' into 'master'

Add back missing index from structure.sql

See merge request gitlab-org/gitlab!45098

db/structure.sql

@@ -20563,6 +20563,8 @@ CREATE INDEX index_issues_on_updated_at ON issues USING btree (updated_at);
 
 CREATE INDEX index_issues_on_updated_by_id ON issues USING btree (updated_by_id) WHERE (updated_by_id IS NOT NULL);
 
+CREATE INDEX index_issues_project_id_issue_type_incident ON issues USING btree (project_id) WHERE (issue_type = 1);
+
 CREATE UNIQUE INDEX index_jira_connect_installations_on_client_key ON jira_connect_installations USING btree (client_key);
 
 CREATE INDEX index_jira_connect_subscriptions_on_namespace_id ON jira_connect_subscriptions USING btree (namespace_id);