Feat(Subcsription): update general error message

What does this MR do and why?

Update the general error message to make it more direct.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Apply this patch that always lets you add a subscription and always fails with the general error message: force-error-on-subscription-add.patch
2. Visit http://localhost:3000/admin/subscription
3. Click the Enter activation code button.
4. Type in any 24-character sting and click Activate

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.