Add finesse to flying snake bite attack.

[chuckhazard]

Fixes #2735

Add finesse property to flying snake bite attack.

[Fyorl]

Rather than setting this one weapon to finesse, perhaps we would be better served by implementing some of the suggestions from #2735? I'd propose that for any weapon of type 'Natural' with the attack ability modifier set to 'Default' that it should use the highest of Str/Dex automatically (min 0). Exceptions could be handled by setting an explicit ability, or by using attack.flat proposed in #2592.

We'd have to evaluate any disruption this might cause for pre-existing Actors using natural weapons but I'm hoping that (a) natural weapons are rare on non-NPCs, and (b) that it will produce the correct result in most cases.

[Fyorl]

Should now be resolved with #5935