nvm: update versions in command description

[reinhart1010]

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• The page is in the correct platform directory (common/, linux/, etc.)
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Version of the command being documented (if known):

From #7511 (comment) by @sbrl:

0.12 and v4.2 are seriously old and unsupported versions of Node.js. Could we update these slightly at all please?

So I decided to update these versions to reflect newer versions of Node.js and to standardize documentation with other versions of nvm (#7511, #7512)

[sbrl]

Thanks, @reinhart1010!