GitHub integration completion page unpolished

[emyller]

For context: the first step of setting up the GitHub integration opens this small popup window:

The problem manifests because we reuse the full page layout in this small windows as last step.

Acceptance criteria

• GitHub integration completion page layout is empty, and should only display the text, emphasised: "GitHub installation completed!"
• Optional: add "you may close this window" in smaller print.

[mustafajw07]

@matthewelwell @emyller Can i contribute for this? Can you assign this to me

[matthewelwell]

Sure, done!

[mustafajw07]

@matthewelwell i have created a pr: #7202

[mustafajw07]

@emyller can you help me test this out, i made the changes but not able to run the github integration in my local.