rebase: fix code comment to refer to right issue (4504, not 4505)

rebase: fix code comment to refer to right issue (4504, not 4505)

The comment was introduced in 8a544fb645bb (rebase: ensure rebase
revision remains visible (issue4504), 2015-01-27), which mentions the
right issue in the description.

--- a/hgext/rebase.py	Wed Feb 01 11:30:26 2017 -0600
+++ b/hgext/rebase.py	Wed Feb 01 08:47:27 2017 -0800
@@ -1367,7 +1367,7 @@
     """store the currently rebased set on the repo object
 
     This is used by another function to prevent rebased revision to because
-    hidden (see issue4505)"""
+    hidden (see issue4504)"""
     repo = repo.unfiltered()
     revs = set(revs)
     repo._rebaseset = revs
@@ -1383,7 +1383,7 @@
         del repo._rebaseset
 
 def _rebasedvisible(orig, repo):
-    """ensure rebased revs stay visible (see issue4505)"""
+    """ensure rebased revs stay visible (see issue4504)"""
     blockers = orig(repo)
     blockers.update(getattr(repo, '_rebaseset', ()))
     return blockers