Fix deprecated tutorial links in DDP tutorial

[patrocinio]

Replace deprecated dist_tuto.html links with current recommended resources:

• Link to PyTorch Distributed Overview for process group setup
• Link to official torch.distributed docs instead of old tutorial

Fixes #3526

Description

Checklist

• [ ] The issue that is being fixed is referred in the description (see above "Fixes #ISSUE_NUMBER")
• [ ] Only one issue is addressed in this pull request
• [ ] Labels from the issue that this PR is fixing are added to this pull request
• [ ] No unnecessary issues are included into this pull request.

cc @svekars @sekyondaMeta @AlannaBurke @wconstab @osalpekar @H-Huang @kwen2501