lint: don't let "insecure gradlew" throw an error
This is a real nasty thing when doing bigger "batch cleanups" on fdroiddata: there's always some old (often no longer maintained) app with an "insecure gradlew" causing lint to stop checking. If I push a batch of 20+ commits and this app was at position 5 – the other 15 commits won't go through lint anymore. And we cannot fix the "insecure gradlew" in the (dead) app's repo.
Hence: a warning is appreciated (especially when integrating a new app – but then the bot had told that before if it came in via RFP). But let lint continue then, and not error-and-stop. It doesn't affect us anyway, so why?