[BUG] The version manager does not respect the NO_PROXY environment variable.

🐛 Bug Report:

Describe the bug

The version manager does not respect the NO_PROXY environment variable. When using the openapi-generator-cli behind a corporate proxy (i.e. HTTP_PROXY & HTTPS_PROXY are set) while trying to download a version of openapi generator from a private maven repository (which is within the corporate network, i.e. the download should not go through the proxy), the NO_PROXY environment variable is ignored.

Steps to Reproduce

Steps to reproduce the behavior:

1. Use the openapi-generator-cli version manager to download a version from a private repository within a corporate network, which is separated from the internet by a proxy.
2. openapi-generator-cli respects HTTP_PROXY & HTTPS_PROXY (which are needed for requests from within the corporate network to the internet, but fails to download from the internal maven repo, as it still tries to go through the proxy:

> openapi-generator-cli generate

Download 6.0.0 ...
Download failed, because of: "socket hang up"

3. Only by explicitly un-setting the HTTP_PROXY & HTTPS_PROXY environment variables as a work-around it is possible to download from the private repo.

Expected behavior

The openapi-generator-cli version manager should respect the NO_PROXY environment variable and download the version of openapi generator from the private repo without going through the proxy.

Additional context

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