edits to NIM 2.20 docs and install script

[travisamartin]

Proposed changes

This PR makes some edits to the NIM 2.20 docs that came in after the release.

[github-actions]

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[github-actions]

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1 out of 2 committers have signed the CLA.
✅ (travisamartin)[https://github.com/travisamartin]
❌ @Chetan-99
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