Fix netlify config to use a git-proxy.finos.org sub-domain for previews

[kriswest]

Describe the bug

Previews of website builds currently come out on netlify domains, e.g. https://deploy-preview-1298--endearing-brigadeiros-63f9d0.netlify.app/

Some enterprises (particularly financial orgs) block netlify.com as it can be used to host arbitrary content, meaning maintainers from those orgs can't view the previews.

Correct the netlify configuration to use a subdomain of git-proxy.finos.org. AFAIK this change can only be made by FINOS, hence, assigning to @TheJuanAndOnly99

[TheJuanAndOnly99]

Hi @kriswest I have configured it so previews will deploy on git-proxy.preview.finos.org. For example see https://deploy-preview-1298.git-proxy.preview.finos.org/.

[kriswest]

Thank you sir!