fixed regex as it wasn't finding any matches

using the following `manifest.json` 

```json
{
  "name": "TestApp",
  "author": {
    "name": "Bulkan Evcimen",
    "email": "bulkan@gmail.com"
  },
  "defaultLocale": "en",
  "private": true,
  "singleInstall": false,
  "location": ["user_sidebar"],
  "version": "1.0.0",
  "frameworkVersion": "0.5",
  "parameters": [
    {
      "name": "backend",
      "type": "text",
      "required": true,
      "default": "https://example.com:3000"
    }
}
```

running `zat server --path /testapp` will zat will prompt for user input to set the _backend_ setting. All user input is treated as invalid. 

IMO I think text fields should accept all data and should be up to the Zendesk app developer to check to see if the value is valid.

This commit fixes this issue by accepting all data.