apex up doesnt support node 12

## Prerequisites

* [ ] I am running the latest version. (`up upgrade`)
* [x] I searched to see if the issue already exists.
* [x] I inspected the verbose debug output with the `-v, --verbose` flag.
* [ ] Are you an Up Pro subscriber?

## Description

Hello,
I added new code to our backend and it contained the not so new private class fields. Everything worked fine locally, running the same runtime version.

## Steps to Reproduce

using up v1.5.1
add any private class fields like:

```
class Test {
#result;
constructor(result) {
this.#result = result;
}
}
```

deploy live
inspect with:
`up logs
`

After a couple of hours debugging this, I had to refactor the class to the old syntax. and everything worked.

Hopefully we won't run into this problem again when we decide to upgrade to node12.

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