Add Node 16 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

Parse Server does not pass Node 16 in the CI, even though it's the current LTS version of node.

Feature / Enhancement Description

Make Parse Server pass Node 16 CI, remove Node 15 support as it's already deprecated.
See #7558.

Example Use Case

n/a

Alternatives / Workarounds

n/a

[parse-github-assistant]

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[mtrezza]

Closing via #7707