chore: Remove unused [tool.black] and [tool.pycln] config (apache#2891)

# Rationale for this change

This PR removes [tool.black] from pyproject.toml. This is an unused
config since formatting now lives in
[ruff.toml](https://github.com/apache/iceberg-python/blob/main/ruff.toml).
Also, updates contributing.md to reference ruff instead of black.

This PR removes dead config from pyproject.toml:
- [tool.black] - replaced by ruff-format apache#127
- [tool.pycln] - replaced by ruff apache#1485 

Also updates contributing.md to reference ruff instead of black.

## Are these changes tested?

Yes

## Are there any user-facing changes?

No

Author: geruh

mkdocs/docs/contributing.md

@@ -118,7 +118,7 @@ make lint
 
 In addition to manually running `make lint`, you can install the pre-commit hooks in your local repo with `prek install`. By doing this, linting is run automatically every time you make a commit.
 
-You can bump the integrations to the latest version using `prek auto-update`. This will check if there is a newer version of `{black,mypy,isort,...}` and update the yaml.
+You can bump the integrations to the latest version using `prek auto-update`. This will check if there is a newer version of `{ruff,mypy,...}` and update the yaml.
 
 ## Cleaning
 

pyproject.toml

@@ -168,13 +168,6 @@ filterwarnings = [
   "ignore:subprocess.*is still running:ResourceWarning",
 ]
 
-[tool.black]
-line-length = 130
-target-version = ['py38']
-
-[tool.pycln]
-all = true
-
 [tool.mypy]
 mypy_path = "python"
 no_implicit_optional = true