CI: Use sys.executable instead of "python" in subprocess (#57220)

Author: jrmylow

scripts/validate_docstrings.py

@@ -188,7 +188,7 @@ def validate_pep8(self):
             file.write(content)
             file.flush()
             cmd = [
-                "python",
+                sys.executable,
                 "-m",
                 "flake8",
                 "--format=%(row)d\t%(col)d\t%(code)s\t%(text)s",