Site Migrations flow: On "We'll take it from here" screen, remove https:// and trailing slash from source site URL

[sixhours]

On the "We'll take it from here" screen after a user has submitted their credentials, remove the https:// and trailing / from the URL:

[github-actions[bot]]

OpenAI suggested the following labels for this issue:

• [Feature Group] Site Migration: The issue pertains to the site migration flow, specifically adjustments in the URL formatting during the migration process.
• [Feature] Permalinks & Slugs: This feature relates to how URLs are managed and displayed, which is relevant to the removal of 'https://' and the trailing slash.
• [Feature] Site Settings: The adjustments require changes in site settings, particularly the configuration of how URLs are presented to users.