Narwhals v1.5.5

Changes

• Revert "patch: allow lit to broadcast as left operand" (#858)
• patch: allow lit to broadcast as left operand (#854)

✨ Enhancements

• feat: implement when/then/otherwise for PyArrow (#859)
• feat: add when-then-otherwise expression (#588)
• feat: use validate_column_comparand in zip_with (#857)
• feat: make DataFrame.select stricter: non-string columns can only be selected using nw.col (#855)

🛠️ Other improvements

• chore: simplify arrow (#860)

Thank you to all our contributors for making this release possible!
@FBruzzesi, @MarcoGorelli and @aivanoved