util: remove outdated comment about construction overhead

An old implementation of this class (possibly only in my local repo)
allocated nodes in the cache during construction time, making
__init__ slow for large cache capacities. The current implementation
lazily grow the cache size, making this comment wrong.

mercurial/util.py

@@ -540,10 +540,6 b' class lrucachedict(object):'
     we recycle head.prev and make it the new head. Cache accesses result in
     the node being moved to before the existing head and being marked as the
     new head node.
-
-    NOTE: construction of this class doesn't scale well if the cache size
-    is in the thousands. Avoid creating hundreds or thousands of instances
-    with large capacities.
     """
     def __init__(self, max):
         self._cache = {}