Revert "Add new token creation callback page to improve current auth flow for integration purpose"

Created by: abeatrix

Reverts sourcegraph/sourcegraph#35339 to unblock main

ref: https://sourcegraph.slack.com/archives/C07KZF47K/p1653067302562219

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.

Test plan

N/A. Revert