query in migration should read from env vars

[dqian]

backend-postgres-typescript-node-express/src/packages/database/migrations/1582820170145-AddUsersTable.ts

Line 30 in 12428e5

await queryRunner.query(`select app_audit.audit_table('${tableName}')`)

this line should be updated to

await queryRunner.query(`select ${config.DB.AUDIT_SCHEMA}.audit_table('${tableName}')`)