[code-infra] Update Babel config to match closer to Core

[oliviertassinari]

Replicate mui/material-ui#43286. I got confused by this comment: "This change is already done in X but I haven't had time to do it here as well." I didn't see where.

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[mui-bot]

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[oliviertassinari]

Arf, the CI fails, harder than I thought.

[romgrk]

I got confused by this comment: "This change is already done in X but I haven't had time to do it here as well." I didn't see where.

There should be a [core] PR on MUI-X with the same change, a while ago. Not sure if I used { loose: true } or the assumptions. I don't think it's worth messing with the config as long as we're already using { loose: true }.

[oliviertassinari]

It would be great to align the babel config to all be the same, something broke when I did it, but yeah, no time on my end to dive into what broke. We use loose, it's likely ok.