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]'

hgext/sparse.py

@@ -374,7 +374,7 b' def debugsparse(ui, repo, **opts):'
     if refresh:
         try:
             wlock = repo.wlock()
-            fcounts = map(
+            fcounts = pycompat.maplist(
                 len,
                 sparse.refreshwdir(
                     repo, repo.status(), sparse.matcher(repo), force=force