localrepo: remove unneeded os.unlink call in wwrite

The opener already unlinks the filename before 'w'riting, for both
the symlink and the normal file case. It also now resets the flags
for normal files on 'w'rite, which makes this os.unlink call completely
redundant.

For Windows, removing this extra unlink call helps to avoid tripping
issue2524 (os.unlink followed by a write).

mercurial/localrepo.py

@@ -629,10 +629,6 @@ class localrepository(repo.repository):
 
     def wwrite(self, filename, data, flags):
         data = self._filter(self._decodefilterpats, filename, data)
-        try:
-            os.unlink(self.wjoin(filename))
-        except OSError:
-            pass
         if 'l' in flags:
             self.wopener.symlink(data, filename)
         else: