bpo-30121: Fix test_subprocess for Windows Debug builds (GH-5758)

(cherry picked from commit 5537646b)
Co-authored-by: Zachary Ware <zachary.ware@gmail.com>

Lib/test/test_subprocess.py

@@ -1183,7 +1183,7 @@ class ProcessTestCase(BaseTestCase):
                 msvcrt.CrtSetReportFile(report_type, msvcrt.CRTDBG_FILE_STDERR)
 
             try:
-                subprocess.Popen([cmd],
+                subprocess.Popen(cmd,
                                  stdout=subprocess.PIPE,
                                  stderr=subprocess.PIPE)
             except OSError: