Claiming Burroughs from AI with Polarity Device doesn't return relic die

[Atticus]

When playing 2-player with the Spacer AI, claiming Burroughs Desert by discarding Polarity Device doesn't return the relic die to the board. Instead, the AI continues to use it for the rest of the game.

Reproduced twice:

1. I had 1 colony on Herbert Valley
2. AI had 1 colony on Burroughs Desert
3. AI had rolled the relic die at least once (may not be relevant)
4. I discarded Polarity Device on my turn, selected Herbert then Burroughs
5. Colonies swapped leaving me with the sole colony on Burroughs Desert. However, the relic die remained in the AI dice pool. Destroying the relic die with Plasma Cannon (not the discard ability) had no effect.

[Clint Herron]

Discarding Polarity Device to take control of Burroughs Desert will now relinquish control of the Artifact Ship from the previous owner. Fixes issue #11

→ 91e16dde591c

[Clint Herron]

Great bug description, thanks so much! Fixed in an internal commit -- this will be included in the upcoming patch release.