Remove Black-specific Python target-version configuration

Since Black's 23.1.0 release it infers the target versions via the project
metadata (python-requires). Verified that it detects this correctly:

    $ black -v src
    [...]
    target_version: ['py310', 'py311']
    [...]

See psf/black#3219

pyproject.toml

@@ -35,7 +35,7 @@ dependencies = [
 
 [project.optional-dependencies]
 development = [
-    "black",
+    "black>=23.1.0",
     "build",
     "mypy",
     "pytest-asyncio",
@@ -171,11 +171,6 @@ required-imports = [
     "from __future__ import annotations",
 ]
 
-[tool.black]
-# This option takes *multiple* Python versions and should include all supported Python
-# versions, but this may change in the future. https://github.com/psf/black/issues/751
-target-version = ["py310", "py311"]
-
 [tool.mypy]
 strict = true
 namespace_packages = true