[python/flask] Pin Werkzeug version (#9638)

This fixes the failing flask test because Werkzeug version 3 removed
`url_quote` raising:

    ImportError: cannot import name 'url_quote' from 'werkzeug.urls'

Author: p8

frameworks/Python/flask/requirements.txt

@@ -10,3 +10,4 @@ Jinja2==3.1.4
 MarkupSafe==2.1.2
 ujson==5.4.0
 orjson==3.8.7; implementation_name=='cpython' 
+Werkzeug==2.3.8