Update tox.ini for a valid "isort" version (#11667)

### Py: Update tox.ini for a valid "isort" version

isort ``5.11.5`` is the latest valid version for Python 3.7, which is the minimum supported Python version.

Author: mdmintz

py/tox.ini

@@ -35,7 +35,8 @@ force_single_line = True
 ; checks linting for CI with stricter exiting when failing.
 skip_install = true
 deps =
-  isort==5.12.0
+  ; isort 5.12+ requires python3.8+ specifically.
+  isort==5.11.5
   black==23.1.0
   ; flake8 6+ requires python3.8+ specifically.
   flake8==5.0.4
@@ -55,7 +56,8 @@ commands =
 ; IMPORTANT: black & isort rewrite files, flake8 merely alerts to the failure.
 skip_install = true
 deps =
-  isort==5.12.0
+  ; isort 5.12+ requires python3.8+ specifically.
+  isort==5.11.5
   black==23.1.0
   ; flake8 6+ requires python3.8+ specifically.
   flake8==5.0.4