Task/update nodesource script

[brendanbond]

Link to Jira Ticket (if applicable)

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Description

The NodeSource installation script has been deprecated, which means pdf-libs and pdf-server no longer receive up-to-date versions of NodeJS. This PR updates the NodeJS installation instructions to conform to the new installation instructions.

Dependencies

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How has this PR been tested?

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Checklist:

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• My changes include tests that prove my fix is effective (or that my feature works as intended)
• New and existing unit/integration tests pass locally with my changes
• Any dependent changes have corresponding PRs that are listed above