Remove Node 12 support

[mtrezza]

New Feature / Enhancement Checklist

• I am not disclosing a vulnerability.
• I am not just asking a question.
• I have searched through existing issues.

Current Limitation

Node 12 it out of LTS, but still tested in CI and range in node engine

Feature / Enhancement Description

Remove node 12 support

Removing Parse Server compatibility would be a breaking change, so this can only be done in Parse Server 6.

Example Use Case

n/a

Alternatives / Workarounds

n/a

[parse-github-assistant]

Thanks for opening this issue!

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[mtrezza]

Dependency PRs already begin to require Node 14, such as #2228. They can't be merged until we drop Node 12 support.

[mtrezza]

Closed via #2277