One way that might (yes, might, I haven't tried this) work is to find which sound is being used and replace it with an empty sound (\common\null.wav, I believe is one).
So (possibly) you'd just copy \common\null.wav into the file location where \items\func_regenerate.wav is normally, rename it func_regenerate.wav and if it works, pakrat it in, and done.
You will likely have to extract null.wav from the TF2 GCF.