Handle the version bump into the main branch

@tmaczukin comment:

If you do that on stable branch, it will then affect version string created when building the patch releases. So, for example, in this case on 17-5-stable you've bumped the VERSION file to 17.6.0. Fortunately, if we're releasing a tag, we're using the tag value explicitly. But any binaries built from commits added to 17-5-stable that are not for the future 17.5.x tags, will report a version of 17.6.0-pre... instead of 17.5.1-pre....
That's not a huge problem, but we should handle it at some moment.
If we want to bump the version on the x-y-stable branch, it should be bumped to the next potential patch release version. And bump to the next major.minor.0 should be done on main just after we've create the incoming release's x-y-stable branch :slightly_smiling_face: