Add `status: possibility` label to the exempt list in stale.yml
Add `status: possibility` label to the exempt list in stale.yml

This help differentiate something between accepted and maybe without
marking the issue as stale.

DemonWav/MinecraftDevIntelliJ,minecraft-dev/MinecraftDev,minecraft-dev/MinecraftDev,DemonWav/MinecraftDevIntelliJ,minecraft-dev/MinecraftDev,DemonWav/IntelliJBukkitSupport,DemonWav/MinecraftDevIntelliJ