fix(debug_manager_xbus): resolve "env._t is not a function" error in `openXbusMessage`

Issue:

An error occurred when env._t was invoked as a function within the openXbusMessage method: TypeError: env._t is not a function at openXbusMessage (debug_manager_xbus.js:33).

Fix:

Replaced the usage of env._t with the imported _t utility from @web/core/l10n/translation.