That you want to use splice tells me you know the index you want to delete. As such, it seems the me the following will do the trick:

AV* av;
I32 i;  // to delete

I32 p = i;
I32 c = av_len(AV) - i;

while (p++, c--) {
    ...move from p to p-1...
}

...shrink the array by one...
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