TursoDB Provider removed support for sqlite-vss

[mikewaters]

FYI, Turso has deprecated sqlite-vss in favor of sqlite-vec, and only support this extension for Pro and Enterprise accounts on fly.io.

Trying to use either vss0 or vec0 virtual tables with standard Turso will not work, and so the provided examples will not support a TursoDB backing SQLiteVSS.

Potential workaround: I've edited the vector[...].sql file to use their native vector type - per #40 - maybe it'll work maybe it won't (I've just started playing around with this today).

Thanks!