Replace flake8-rst with flake8-rst-docstrings
Fixes #46865

Replace `flake8-rst` with `flake8-rst-docstrings` for running flake8 on code snippets in rst files.

* **pyproject.toml**
  - Remove `flake8` from the `tool.ruff.lint` section.
  - Add `flake8-rst-docstrings` to the `tool.ruff.lint` section.
  - Update the `tool.ruff.lint` section to use `flake8-rst-docstrings` instead of `flake8-rst`.

* **.pre-commit-config.yaml**
  - Remove the `flake8-rst` hook from the `hooks` section.
  - Add a new hook for `flake8-rst-docstrings` in the `hooks` section.
  - Configure the new `flake8-rst-docstrings` hook with appropriate `additional_dependencies`.

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For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/pandas-dev/pandas/pull/60654?shareId=89ddda75-4f5f-4ddf-87d1-3b3afb809a56).
This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this. Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen.