fix: allow any name in expression parsing

[FBruzzesi]

Currently if we do:

@nw.narwhalify
def func(df):
    return df.with_columns(df=nw.col("a")+1)

with any backend except polars, we get an error:

TypeError: evaluate_into_exprs() got multiple values for argument 'df'

This PR fixes this issue

What type of PR is this? (check all applicable)

• 💾 Refactor
• ✨ Feature
• 🐛 Bug Fix
• 🔧 Optimization
• 📝 Documentation
• ✅ Test
• 🐳 Other

[MarcoGorelli]

you win an award for spotting this 🏆