bundlespec: fix the "streamv2" and "streamv3-exp" variant
In c4aab3661f25, we broken this feature by adding unicode instead of bytes to
the dictionary.
On the other hand, this feature was never tested, so augment the tests to tests
this.
= Mercurial XXX =
== New Features ==
== Default Format Change ==
These changes affect newly created repositories (or new clones) done with
Mercurial XXX.
== New Experimental Features ==
== Bug Fixes ==
== Backwards Compatibility Changes ==
== Internal API Changes ==
== Miscellaneous ==