Improve Concussion Rocket promotion popup

[copyrite]

⚠️ I have not tested this, please build and verify before merging ⚠️

There's still room to improve on at least these:

• Mention improved accuracy over standard rocket
• Test & explain effect on Chosen, mechanicals and Psi Zombies
• Figure out what the hell is an Elite Codex
• Possibly awkward wording on the Disorient bullet