fix proxy resolution

[kentac55]

fix #160

I don't know how I can check it work correctly, but I confirmed as below:

1. yarn build
2. cp lib/index.js ~/.config/coc/extensions/node_modules/coc-python/lib
3. http_proxy=http://myproxy:8080 https_proxy=http://myproxy:8080 nvim a.py
4. :CocCommand then choose python.upgradePythonLanguageServer
5. finished correctly

my coc-settings.json:

{
  "diagnostic.displayByAle": true,
  "languageserver": {
    "go": {
      "command": "gopls",
      "args": [],
      "rootPatterns": ["go.mod", ".git/"],
      "filetypes": ["go"]
    },
    "metals": {
      "command": "metals-vim",
      "rootPatterns": ["build.sbt"],
      "filetypes": ["scala", "sbt"]
    }
  },
  "python.jediEnabled": false,
  "python.linting.enabled": false,
  "suggest.timeout": 5000
}

[g-i-o-r-g-i-o]

not working with vim 8.2 and proxy