Two (possible) improvements at dataclasses.rst

Documentation

Observed two possible improvements at dataclasses.rst

1. One of the examples at line 705 is throwing an exception. I would kindly suggest to update x: List = [] by x: list = field(default_factory=list) to avoid the following exception: ValueError: mutable default <class 'list'> for field x is not allowed: use default_factory
2. Remove trailing whitespace in line 745 to avoid exception with automated Azure PR Validation.

@ericvsmith I would be more than happy to raise a PR for above.

Linked PRs

• gh-91687: fix dataclass example typing #103773
• [3.11] gh-91687: modernize dataclass example typing (GH-103773) #103774