requirements[dev]: Clarify black version to synchronize Python support.

Author: neiljp

setup.py

@@ -30,7 +30,7 @@ def long_description():
 
 linting_deps = [
     "isort~=5.11.0,<5.12.0",  # 5.12.0 drops support for Python 3.7, 6.0.0 drops 3.8
-    "black~=23.0",
+    "black==23.3.0",  # Later versions drop support for Python 3.7
     "ruff==0.0.267",
     "codespell[toml]~=2.2.5",
     "typos~=1.16.11",