Remove update_json_schema (bad practice func)

[sydney-runkle]

Fix #8381

Removing a function that was minimally used, and was following bad practice. This function was problematic in that it both:

1. Modified an argument in place
2. Returned said modified argument

This is technically a change (bc the update_json_schema func was public), but I'm not too concerned about this - it was a think wrapper around the some_dict.update function, so it can easily be replaced. I've marked this as relnotes-change accordingly, and will draw attention to this in the release notes.

Selected Reviewer: @alexmojaki

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[sydney-runkle]

Please review

[codspeed-hq]

CodSpeed Performance Report

Merging #9125 will not alter performance

_{Comparing remove_old_json_schema_func (39075f3) with main (b30f44d)}

Summary

✅ 13 untouched benchmarks

[alexmojaki]

I think this is OK to merge, but I will point out that @dmontagu and the issue title said to deprecate the function, not remove it.