Clean up obsolete TODO for _setGitSsh()

Change Idcc9808948b018a271b32492766a96876979d1fa addressed the need
for connection context in zuul.merger.merger.Merger.updateRepo() but
failed to remove the TODO comment associated with it. Clean up the
unnecessary comment now.

Change-Id: I57a48a27a09b39efdc4d15f1a3a674b83a1d1199
1 file changed