Use type 'string' instead of 'str'

Author: colesbury

.github/workflows/build-python-packages.yml

@@ -15,7 +15,7 @@ on:
       THREADING_BUILD_MODES:
         description: 'CPython threading build modes'
         required: true
-        type: str
+        type: string
         default: 'freethreaded'
       PLATFORMS:
         description: 'Platforms for execution in "os" or "os_arch" format (arch is "x64" by default)'