[TF2] Restored unused Rocket Destroyed voice response

[rabscootle]

Resolves ValveSoftware/Source-1-Games#5925

Updated tf_weapon_minigun.cpp to include a trigger for unused MP_CONCEPT_ROCKET_DESTOYED concept. RocketDestroyedHeavy response rule will now play in-game.

Recommended to also update scripts/talker/heavy.txt with the following changes:

• Lower frequency of rocket deflect vo (50% -> 10%)
• Add "IsDominating" context to ensure voicelines are not truncated by taking damage

An updated response rule with these changes incorporated can be found below:

Response RocketDestroyedHeavy
{
     scene "scenes/Player/Heavy/low/3979.vcd"
     scene "scenes/Player/Heavy/low/3980.vcd"
     scene "scenes/Player/Heavy/low/3982.vcd"
}
Rule RocketDestroyedHeavy
{
     criteria ConceptRocketDestroyed 10PercentChance IsHeavy
     ApplyContext "IsDominating:1:5" // Adding this so Heavy doesn't get cut off when taking damage
     Response RocketDestroyedHeavy
}

heavy_deflect_fix.mp4

Description