fix: fix duplicate httpProxy option setup

It looks like there was an `httpProxy` option and an `http-proxy` option but these got
accidentally(?) squashed into a duplicated `httpProxy` option in
https://github.com/netlify/cli/pull/5816/files#diff-6708246L106-L140.

Author: serhalp

src/commands/base-command.ts

@@ -190,11 +190,6 @@ export default class BaseCommand extends Command {
       .addOption(new Option('--cwd <cwd>').hideHelp(true))
       .addOption(new Option('-o, --offline').hideHelp(true))
       .addOption(new Option('--auth <token>', 'Netlify auth token').hideHelp(true))
-      .addOption(
-        new Option('--httpProxy [address]', 'Old, prefer --http-proxy. Proxy server address to route requests through.')
-          .default(process.env.HTTP_PROXY || process.env.HTTPS_PROXY)
-          .hideHelp(true),
-      )
       .addOption(
         new Option(
           '--httpProxyCertificateFilename [file]',