gh-120513: Add thread-safety warning to os.environ docs

[hrimov]

• Issue: Documentation for os.environ should say that os.environ caching behavior is undefined if other threads are setting environment values #120513

[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #33432353 | 📁 Comparing e8efe61 against main (423ae0f)

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1 file changed

± library/os.html