Fix targeting

[KheirFerrum]

Summary

SUMMARY: Bugfixes "Fix targeting"

Purpose of change

Fixes #2567.

Issue was that there's a Character variable and Player variable last_target and last_target_pos, so in aim_activity_actor::finish() the game was checking the wrong variable and resetting the wrong variable.

Describe the solution

Remove unused Character variables last_target and last_target_pos. Fix consideration in aim_activity_actor::finish() so it'll check and update correct variable.

Describe alternatives you've considered

• Move variable to Character class
  • Good eventual goal. Not doing it here because it'd require fixing up save_game_json.cpp and would probably be better as part of a Player to Character migration.

Testing

Spawn 5 decayed zombies and wield an M4A1. Save

• Kill all 5 zombies with gun at range without exiting aim, check that cursor never lingers on dead targets.
• Reload from previous save and test again 5 times.

Additional context

[scarf005]

targeting.mp4

confirmed that the targeting works as intended. LGTM