Documentation

os.environ docs don't mention that the keys get upper-cased automatically on e.g. Windows.

Linked PRs

• gh-101754: document that on Windows, keys in os.environ are converted to uppercase #101840
• [3.10] gh-101754: Document that Windows converts keys in os.environ to uppercase (GH-101840) #102393
• [3.11] gh-101754: Document that Windows converts keys in os.environ to uppercase (GH-101840) #102394