fix(server): disable let syntax when not supported

[crisbeto]

Disables the @let syntax for projects that run an Angular version less than 18.1.

[angular-automatic-lock-bot[bot]]

This issue has been automatically locked due to inactivity. Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}