pref75: corrige une erreur de syntaxe avec python <= 3.11

Attrap_pref75.py

@@ -60,7 +60,7 @@ class Attrap_pref75(Attrap):
                 False
             )[::-1]
             for month_page in month_pages:
-                month_date = Attrap.guess_date(f'{month_page['name']} {year}', "(.*)").replace(day=1)
+                month_date = Attrap.guess_date(f"{month_page['name']} {year}", "(.*)").replace(day=1)
                 if month_date >= self.not_before.replace(day=1):
                     pages_to_parse.append(month_page['url'])