[3.12] gh-102856: Add missing quote to fix doctest (GH-104852)

[miss-islington]

(cherry picked from commit 3e97c00)

Co-authored-by: Hugo van Kemenade [email protected]

• Issue: PEP 701 – Syntactic formalization of f-strings #102856

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📚 Documentation preview 📚: https://cpython-previews--104854.org.readthedocs.build/

[hugovk]

I didn't expect that to auto-merge so soon, it's because the CI docs checks aren't required. I'll check they pass :)

Edit: ✅