bundle: do no check the changegroup version if no changegroup is included
We don't need to check the compatibility of something we will not use.
In practice this was getting in the was of `streamv2` bundles on a narrow
repository as the 'cg.version=02' value was rejected by this checks.
/assign_reviewer @mercurial.review
<!--
Welcome to the Mercurial Merge Request creation process:
* Set a simple title for your MR,
* All important information should be contained in your changesets' content or description,
* You can add some workflow-relevant information here (eg: when this depends on another MR),
* If your changes are not ready for review yet, click `Start the title with Draft:` under the title.
More details here:
* https://www.mercurial-scm.org/wiki/ContributingChanges
* https://www.mercurial-scm.org/wiki/Heptapod
-->