Add rollbackPackageHealthObserverTest to presubmit

It first needs the test to be in postsubmit to run SLO chacks. Once that
passes we can add it to presubmit in a later CL.

Test: config change
Bug: 291137901
Change-Id: Ie5f9d404a84c4a16e791cac5fc0a6b867561a67f