[GAME] Vortigaunts and zombigaunts create orphaned env_physexplosion entities during dispel attacks

[1upD]

Describe the bug

When making dispel attacks, vortigaunts and zombigaunts use an env_physexplosion entity to apply physics forces to objects in the attack's AOE.

The env_physexplosion spawned is never cleaned. If someone was to make an infinite wave map (possibly Christmas themed) which spawns vortigaunts and zombigaunts, each dispel attack would add another entity to the map until the maximum amount of entities are reached.

Steps to reproduce

Steps to reproduce the behavior:

1. Play Operation Xmas Lapland by entering map ez2_op_xmas_lapland in the console. The map may need to be recompiled. (Recommend compiling from the developer workspace)
2. After a zombie wave or vortigaunt hit squad wave, run report_entities to list all entities in the map. There will be some env_physexplosion entities in the list.
3. Repeat step 2 and observe that with each dispel attack, more env_physexplosion entities are reported. The most I have seen is 180.

Expected behavior

Vortigaunt and zombigaunt attacks should not permanently increase the number of entities in the map.

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