chore: drop Python2-specific aliases

Author: tseaver

google/api_core/page_iterator.py

@@ -125,7 +125,7 @@ def __iter__(self):
         """The :class:`Page` is an iterator of items."""
         return self
 
-    def next(self):
+    def __next__(self):
         """Get the next value in the page."""
         item = next(self._item_iter)
         result = self._item_to_value(self._parent, item)
@@ -134,9 +134,6 @@ def next(self):
         self._remaining -= 1
         return result
 
-    # Alias needed for Python 2/3 support.
-    __next__ = next
-
 
 def _item_to_value_identity(iterator, item):
     """An item to value transformer that returns the item un-changed."""
@@ -232,9 +229,6 @@ def __next__(self):
             self.__active_iterator = iter(self)
         return next(self.__active_iterator)
 
-    # Preserve Python 2 compatibility.
-    next = __next__
-
     def _page_iter(self, increment):
         """Generator of pages of API responses.