Downsample defeat2.ogg and victory2.ogg from 48 KHz to 44.1 KHz

44.1 KHz is the standard used for all other Wesnoth tracks and it's the
default sample rate used by SDL_Mixer. Playing music with any other
sample rate at 44.1 KHz results in sound distortion of sorts (in this
case, the pitch changes) since SDL_Mixer cannot do resampling. This
leads to music tracks not sounding as intended by the artist when played
in-game.

I dealt with this issue ages ago and claimed there weren't any tracks
left with nonstandard sample rates, but it seems I just overlooked these
two.