Fix node version detection in nvm_install_latest_npm

[todeveni]

nvm_version_greater 20.17.0 v22.14.0 exits with code 3 and nvm thinks node version is NVM_IS_20_5_OR_ABOVE thinking npm@10 is the latest compatible with 22.14.0.

Switch to nvm_version_greater_than_or_equal_to and for consistency change NVM_IS_20_17_or_ABOVE variable to uppercase.

Before patch

$ nvm version
v22.14.0
$ nvm install-latest-npm
Attempting to upgrade to the latest working version of npm...
* `npm` `v10.x` is the last version that works on `node` `< v20.17`, `v21`, or `v22.0` - `v22.8`

After patch

$ nvm version
v22.14.0
$ nvm install-latest-npm
Attempting to upgrade to the latest working version of npm...
* Installing latest `npm`; if this does not work on your node version, please report a bug!

[ljharb]

thanks, this looks correct