Fix doc to use new callback url for spa

CONTRIBUTING.md

@@ -32,7 +32,7 @@ Create a new [GitHub App](https://github.com/settings/apps), setting the followi
 
 - **GitHub App name**: Anything you want, but it must be unique across GitHub
 - **Homepage URL**: `https://github.com/apps/GITHUB_APP_NAME` (The full URL to your GitHub App’s website)
-- **Callback URL**: `https://DOMAIN/github/callback`
+- **Callback URL**: `https://DOMAIN/rest/app/cloud/github-callback`
 - **Setup URL**: `https://DOMAIN/github/setup`
 - **Webhook URL**: `https://DOMAIN/github/webhooks`
 - **Webhook Secret**: `development`
@@ -140,4 +140,4 @@ That being said, here are the steps needed to create a Pull Request for us to re
 1. Commit and Push your changes - verify it passes all checks.
 1. Submit your pull request with a detailed message about what's changed.
 1. Wait for us to review and answer questions/make changes where requested.
-1. Once merged, celebrate with your drink of choice because you've just helped thousands (if not millions) of people get a better experience in both Jira and GitHub! :beers:
+1. Once merged, celebrate with your drink of choice because you've just helped thousands (if not millions) of people get a better experience in both Jira and GitHub! :beers: