remove nvm installation for SDK automation

[kazrael2119]

fixes Azure/azure-sdk-tools#7967

[maorleger]

Rather than removing the installation steps, could we instead check and skip if nvm is already installed?

Edit: I am not that worried about automation_init scripts so feel free to ignore

[wanlwanl]

@raych1 for awareness

[raych1]

@kazrael2119
The code to call NVM to set node version can also be removed since the pipeline agent doesn't have NVM installed.
Both the init script and the generate script are currently only used in the spec PR pipeline which has already installed the Node. We can ignore the NVM/Node installation in these script.

[jeremymeng]

The automation probably don't need to use nvm to switch nodejs versions? Looking at the history nvm was used to install node v18, likely when 18 is not the default installed version.

[jeremymeng]

/cc current code owners @ckairen @mikeharder please let me know if we should have better owners for these files.

[raych1]

The automation probably don't need to use nvm to switch nodejs versions? Looking at the history nvm was used to install node v18, likely when 18 is not the default installed version.

@jeremymeng
This PR is to revert the change added previously to install NVM to install node18 when the spec PR pipeline didn't support node18. The spec PR has already supported the node 18 and it will upgrade the node version per the lifetime. So, it doesn't need the JS language automation script to install node separately.

[wanlwanl]

@jeremymeng @raych1 I found the checkenforcer is always in pending status. but when I click button, the status is already success. could you help merge the pr?

[jeremymeng]

/check-enforcer override