Build fails due to upgrade downstream failure on code coverage check

[mockitoguy]

Build fails due to upgrade downstream failure on code coverage check:

Travis CI link: https://travis-ci.org/github/mockito/shipkit/builds/704857764#L1931 Error:

[upgradeDownstream] [performVersionUpgrade] > Exception happen while trying to merge pull request. Merge aborted. Original issue: Pull request https://api.github.com/repos/mockito/shipkit/pulls/874 cannot be merged. 56.25% of diff hit (target 76.38%). You can check details here: null

I suggest we stop using "upgradeDownstream" and move to dependabot.