Remove namespace select after group create fails during trial creation

What does this MR do and why?

Implements #405125 (closed).

This MR hides the namespace select when the new group option is selected and an error occurs.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Setup to simulate SaaS and restart GDK
2. Visit /-/trials/new when you have more than 1 trial eligible namespace
3. Fill in company information and submit, or just skip to -/trials/new?step=trial
4. Select Create group from the namespace selector
5. Fill in invalid name, like @ _
6. See namespace select is hidden and input has group name populated

MR acceptance checklist

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

Related to #405125 (closed)