types: Add allow_nobody_group field to GroupPermissionSetting.

zerver/lib/types.py

@@ -279,3 +279,4 @@ class GroupPermissionSetting:
     require_system_group: bool
     allow_internet_group: bool
     allow_owners_group: bool
+    allow_nobody_group: bool

zerver/models.py

@@ -2619,6 +2619,7 @@ class Stream(models.Model):
             require_system_group=True,
             allow_internet_group=False,
             allow_owners_group=False,
+            allow_nobody_group=False,
         ),
     }