store: no longer explicitly mark the splitted index as ignored

Since the fncache is going to automatically recognised it as non "normal"
revlog file, we don't need to explicitly make it ignored.

mercurial/revlog.py

@@ -2060,10 +2060,6 b' class revlog:'
             opener = self.opener
             weak_self = weakref.ref(self)
 
-            fncache = getattr(opener, 'fncache', None)
-            if fncache is not None:
-                fncache.addignore(new_index_file_path)
-
             # the "split" index replace the real index when the transaction is finalized
             def finalize_callback(tr):
                 opener.rename(