sparse: fix a py2 based usage of `map()` In a local pytype run, this fixes: File "/mnt/c/Users/Matt/hg/hgext/sparse.py", line 386, in debugsparse: unsupported operand type(s) for item retrieval: 'fcounts: Iterator[int]' and '0: int' [unsupported-operands] No attribute '__getitem__' on 'fcounts: Iterator[int]' File "/mnt/c/Users/Matt/hg/hgext/sparse.py", line 387, in debugsparse: unsupported operand type(s) for item retrieval: 'fcounts: Iterator[int]' and '1: int' [unsupported-operands] No attribute '__getitem__' on 'fcounts: Iterator[int]' File "/mnt/c/Users/Matt/hg/hgext/sparse.py", line 388, in debugsparse: unsupported operand type(s) for item retrieval: 'fcounts: Iterator[int]' and '2: int' [unsupported-operands] No attribute '__getitem__' on 'fcounts: Iterator[int]'