Update mergify configuration. (backport #7385) (#7386)
Update mergify configuration. (backport #7385) (#7386)

Per https://blog.mergify.com/strict-mode-deprecation/, the strict mode
has been deprecated and will be turned off on 10-Jan-2022. This updates
the config to use the new, approved thing instead of the old thing.

(cherry picked from commit 2d4844f97f804149aa6dd47bcf957c1de9eaf6ea)

tendermint/tendermint,tendermint/tendermint,tendermint/tendermint,tendermint/tendermint