fix: msnodesqlv8 connection string uses correct instance name

driver was not using the correct option for instanceName and so it was
undefined rather than the correct value.

Author: partik-mis

lib/msnodesqlv8/connection-pool.js

@@ -24,7 +24,7 @@ class ConnectionPool extends BaseConnectionPool {
       if (!this.config.connectionString) {
         cfg.conn_str = buildConnectionString({
           Driver: CONNECTION_DRIVER,
-          Server: this.config.options.instanceName ? `${this.config.server}\\${this.config.instanceName}` : `${this.config.server},${this.config.port}`,
+          Server: this.config.options.instanceName ? `${this.config.server}\\${this.config.options.instanceName}` : `${this.config.server},${this.config.port}`,
           Database: this.config.database,
           Uid: this.config.user,
           Pwd: this.config.password,