[DOCS] Previewers source code folder URL is pointing to previous Clowder repo

[sandeep-ps]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. Go to previewer documentation page.
2. See the "source" URL pointing to the previous Clowder repo.

Expected behavior
Fix the URL to link to the Clowder GitHub repo.

Additional context
Add any other context about the problem here.