Add warning about leaving migation labels. (#528)
Add warning about leaving migation labels. (#528)

* Add warning about leaving migation labels.

* Move to single line.

bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration