Made the multiple dupe response a little more clear

[Zacatero]

If one or more dupe is already been reported, i changed it to say "One or more of your dupes have already been submitted by another Custodian"

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• [X] I agree to the Contribution Guidelines and to the Code of Conduct
• [X] I tested my code and I verified it's working to the best of my ability
• [X] I checked if my code doesn't violate the styleguide with npm test

Describe your pull request

When you have many dupes in one command, the reply if one of them was already reported was vague. I made

Why is this change needed?

In reference to an issue

Does your pull request solve an open issue? If yes, please mention what one

Fixes #136

[Zacatero]

@Kitty-Therapist idk how to handle your suggestion (I'm on mobile) so I just added it as a commit manually

[Kitty-Therapist]

Looks better now. Thank you. ❤️