Fixes#131535

Back in Python 3.5, the default forconvert_charrefs was changed fromFalse toTrue. One of the docs examples still assumes the old default ofFalse. This PR updates the example to reflect the current behavior.

Also migrates the examples to doctests to help catch any further discrepancies. Slightly tweaks two examples to avoid relying on trailing whitespace, which isn't visible in the output and makes doctests tricky.

• Issue:html.parser produces different output than documented #131535

📚 Documentation preview 📚:https://cpython-previews--131551.org.readthedocs.build/