Specify a valid callback url for github app auth provider

[rak-phillip]

Summary

This specifies a valid callback url for the github app auth provider.

Fixes #15639

Occurred changes and/or fixed issues

• Specify a valid callback url for github app auth provider

Technical notes summary

Copy to clipboard was previous using the server url - we can construct callback url in the component and use that instead.

Areas or cases that should be tested

GitHub App auth provider should contain the correct text when

Areas which could experience regressions

NA

Screenshot/Video

NA

Checklist

• The PR is linked to an issue and the linked issue has a Milestone, or no issue is needed
• The PR has a Milestone
• The PR template has been filled out
• The PR has been self reviewed
• The PR has a reviewer assigned
• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes
• The PR has been reviewed in terms of Accessibility
• The PR has considered, and if applicable tested with, the three Global Roles Admin, Standard User and User Base

[eva-vashkevich]

lgtm