fix(collections): up-to-date lookup for collection_id

It appears something change in the Notion API which causes errors when working with recently created databases. This results in being unable to find the `collection_id` of a `CollectionViewBlock` which has downstream affects such as exceptions when trying to access the `title` property of the database and being unable to add rows to the collection.

This commit changes how the `collection_id` is retrieved within the `CollectionViewBlock` class such that the lookup succeeds for newish and oldish databases.

Fixes jamalex#367

notion/block.py

@@ -714,7 +714,7 @@ class CollectionViewBlock(MediaBlock):
 
     @property
     def collection(self):
-        collection_id = self.get("collection_id")
+        collection_id = self.get("format.collection_pointer.id")
         if not collection_id:
             return None
         if not hasattr(self, "_collection"):
@@ -725,7 +725,7 @@ def collection(self):
     def collection(self, val):
         if hasattr(self, "_collection"):
             del self._collection
-        self.set("collection_id", val.id)
+        self.set("format.collection_pointer.id", val.id)
 
     @property
     def views(self):