fix: user list in space permissions shows duplicates

[andrewdw]

Closes: #12488

Description:

• Adds deduplication logic to not show the same user more than once in space permissions. This is caused when the user belongs to more than one group.

Reviewer actions

• [ ] I have manually tested the changes in the preview environment
• [ ] I have reviewed the code
• [ ] I understand that "request changes" will block this PR from merging

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