Excluded black from dev for Python 3.7

We excluded black from development dependencies for Python 3.7 as black
dropped support for Python 3.7 (due to its EOL) and only supports Python
versions from 3.8 on.

setup.py

@@ -52,7 +52,6 @@
     extras_require={
         "dev": [
             "pylint==2.13.9",
-            "black==23.9.1",
             "tox>=3.0.0",
             "pydocstyle>=6.1.1,<7",
             "coverage>=4.5.1,<5",
@@ -66,6 +65,7 @@
             "numpy>=1,<2",
         ]
         + (["mypy==1.5.1"] if sys.version_info >= (3, 8) else [])
+        + (["black==23.9.1"] if sys.version_info >= (3, 8) else [])
         + (["deal==4.23.3"] if sys.version_info >= (3, 8) else [])
         + (["asyncstdlib==3.9.1"] if sys.version_info >= (3, 8) else []),
     },