filter-repo: ensure we write final newline after final progress update

We try to write 'Parsed %d commits' messages only after enough time has
past to avoid writing to stdout becoming a bottleneck.  However, there
was a slight logic error that would cause it to only print the final
newline if there was a new message since the last progress update,
leaving a small race condition where we might miss it.

Reported-by: Valentyn Shtronda (@valiko-ua)
Signed-off-by: Elijah Newren <newren@gmail.com>

git-filter-repo

@@ -341,7 +341,7 @@ class ProgressWriter(object):
     self._last_progress_update = 0
     if self._last_message:
       self.show(self._last_message)
-      sys.stdout.write("\n")
+    sys.stdout.write("\n")
 
 class _IDs(object):
   """