Revert "Hey, wait a second, that should be default"

I think we had that for a reason like that. Will revert.

This reverts commit 375e447964.

etherpump/commands/pull.py

@@ -166,7 +166,7 @@ def build_argument_parser(args):
     )
     parser.add_argument(
         "--publish-opt-in",
-        default=True,
+        default=False,
         action="store_true",
         help="ensure `--publish` is honoured instead of `--nopublish`",
     )