Normalizes dropship_crash to -6db (#5588)

# About the pull request

Normalizes dropship_crash.ogg to -6db (from 0db). This is still quite
loud (inherently) and punchy at -6db, which should still be louder than
our standard normalization which rests at -8db.

# Explain why it's good for the game

Hijack is so loud.  So very very loud. :(


# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

Listened to the .ogg and waited for my ears to bleed. (They didn't, for
once.)

</details>


# Changelog
:cl:
soundadd: brought dropship_crash down from 0db to -6db
/:cl: