chore: fix api preview indentation

[jessrynkar]

Description

PR for 3.0 here.

Fixes indentation in API response preview for empty nested groups and arrays.

Related #6112

• [X] I have read and understand the CONTRIBUTING.md document in this repository.

Type of change

• [X] Chore (non-breaking change which does not add functionality)

Checklist:

• [X] Existing test suite passes locally with my changes