Update pydantic-settings docs

[hramezani]

This will update pydantic-settings doc.

@sydney-runkle do we need extra steps to make the change available on docs.pydantic.dev?

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[codspeed-hq]

CodSpeed Performance Report

Merging #8906 will not alter performance

_{⚠️ No base runs were found}

_{Falling back to comparing update-pydantic-settings-doc (20db45c) with main (752daaf)}

Summary

✅ 10 untouched benchmarks

[sydney-runkle]

@hramezani,

Let's merge into main, then I'll cherry-pick this over for the 2.6.3 release soon 👍. Could you make that change when you have a chance? Thanks!

[sydney-runkle]

Update - we want main to point to latest, so I'm merging this into the 2.6 branch to be released with our v2.6.3 changes.