text: Title: relationship_proxy documentation doesn't work with `_: dataclasses.KW_ONLY`
  Body: ### Describe the bug
  
  Consider the example [here](https://docs.sqlalchemy.org/en/20/orm/extensions/associationproxy.html#simplifying-association-objects):
  
  If you add `MappedAsDataclass` and `_: dataclasses.KW_ONLY` to `UserKeywordAssociation` the example stops working because the implicit creator passes the argument as positional.
  
  ### Optional link from https://docs.sqlalchemy.org which documents the behavior that is expected
  
  _No response_
  
  ### SQLAlchemy Version in Use
  
  2.0.31
  
  ### DBAPI (i.e. the database driver)
  
  asyncpg
  
  ### Database Vendor and Major Version
  
  postgres 16
  
  ### Python Version
  
  3.12
  
  ### Operating system
  
  Linux
  
  ### To Reproduce
  
  ```python
  from __future__ import annotations
  
  from typing import List
  from typing import Optional
  
  from sqlalchemy import ForeignKey
  from sqlalchemy import String
  from sqlalchemy.ext.associationproxy import association_proxy
  from sqlalchemy.ext.associationproxy import AssociationProxy
  from sqlalchemy.orm import DeclarativeBase
  from sqlalchemy.orm import MappedAsDataclass
  from sqlalchemy.orm import Mapped
  from sqlalchemy.orm import mapped_column
  from sqlalchemy.orm import relationship
  
  
  class Base(DeclarativeBase, MappedAsDataclass):
      pass
  
  
  class User(Base):
      __tablename__ = "user"
  
      id: Mapped[int] = mapped_column(primary_key=True)
      name: Mapped[str] = mapped_column(String(64))
  
      user_keyword_associations: Mapped[List[UserKeywordAssociation]] = relationship(
          back_populates="user",
          cascade="all, delete-orphan",
      )
  
      # association proxy of "user_keyword_associations" collection
      # to "keyword" attribute
      keywords: AssociationProxy[List[Keyword]] = association_proxy(
          "user_keyword_associations",
          "keyword",
      )
  
      def __init__(self, name: str):
          self.name = name
  
  
  class UserKeywordAssociation(Base):
      __tablename__ = "user_keyword"
      _: dataclasses.KW_ONLY
      user_id: Mapped[int] = mapped_column(ForeignKey("user.id"), primary_key=True)
      keyword_id: Mapped[int] = mapped_column(ForeignKey("keyword.id"), primary_key=True)
      special_key: Mapped[Optional[str]] = mapped_column(String(50))
  
      user: Mapped[User] = relationship(back_populates="user_keyword_associations")
  
      keyword: Mapped[Keyword] = relationship()
  
  
  class Keyword(Base):
      __tablename__ = "keyword"
      id: Mapped[int] = mapped_column(primary_key=True)
      keyword: Mapped[str] = mapped_column("keyword", String(64))
  
      def __init__(self, keyword: str):
          self.keyword = keyword
  
      def __repr__(self) -> str:
          return f"Keyword({self.keyword!r})"
  
  user = User("log")
  for kw in (Keyword("new_from_blammo"), Keyword("its_big")):
    user.keywords.append(kw) # boom
  print(user.keywords)
  ```
  
  
  ### Error
  
  ```
  /Users/tamird/Library/Caches/pypoetry/virtualenvs/common-hf-Ms37h-py3.12/lib/python3.12/site-packages/sqlalchemy/ext/associationproxy.py:1505: in append                  
      item = self._create(value)                                                                                                                                            
  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _                                                               
                                                                                       
      def _create(self, value: _T) -> Any:                                                                                                                                  
  >       return self.creator(value)                                                                                                                                                                                                                                                                                                                   
  E       TypeError: __init__() takes 1 positional argument but 2 were given    
  ```
  
  ### Additional context
  
  _No response_