fix(api): Restore browsable API JSON indentation

[webjunkie]

Problem

JSON rendering got updated in #20302 with no indents (cause faster)

Changes

We can look at the context to see if we are in the browsable API render.

How did you test this code?

• go to http://localhost:8000/api/projects/1 with browser and see that it looks nice again

[sentry-io]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: posthog/renderers.py

Function	Unhandled Issue
render	TypeError: str is not valid UTF-8: surrogates not allowed /api/projects/{parent_lookup_team_id}/session_recordings/{pk}/s... Event Count: 19

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[sentry-io]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ TypeError: Integer exceeds 64-bit range /api/projects/{parent_lookup_team_id}/persons/ View Issue

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