Dataops-ci-bot should rebase before generating schemas

[fbertsch]

The dataops-ci-bot currently generates schemas for main and HEAD, and compares them. The problem is that sometimes compatible commits will exist on main but not on HEAD, which look like incompatible schema changes when comparing schemas. For example, if there is an additional field on main, it will look like it's missing on HEAD, when in fact it will be added during the rebase commit.

We should first rebase on main before running the integration tests. That will show the actual changes between main and HEAD.