st3m: captouch: Bump the top petal threshold up
Otherwise it's easy to get ghosting on non-touched petals when firmly touching other petals on the top board.
Probably not a proper solution, but it calls for a band-aid anyway since the issue is quite serious - it's very easy to get spurious touch on top petals that aren't actually touched at all when other top petals are pressed firmly. With the current value it's even quite easy to make all top petals appear pressed by only actually touching two of them. The effect was present in 1.2.0 already (and probably earlier too, haven't checked), but got much easier to trigger with captouch changes that got merged soon before tagging 1.3.0 - some songs in Petal Hero became quite hard to play without triggering "ghost" touches, which I initially blamed bad calibration for, but it turned out unrelated upon closer inspection (triggered by me having too much time to pass in a train a few days ago :P). This is made worse by the fact that the first user instinct after noticing ghost touches is to make your grip firmer - which is exactly the wrong reaction in this case.
In my testing, setting top petal threshold to 15000 makes it behave much closer to how 1.2.0 behaved, which so far seems to be a clear improvement - it's much harder to trigger ghost touches (not impossible, but you need to press quite hard), while it's still very sensitive while the flow3r is held in a hand. When it's not held it still seems sensitive enough, although it may not necessarily register a very light fingertip touch as a touch - however, it doesn't seem to have troubles with registering a finger actually well-placed on a petal. 12000 is also a big improvement over 8000, but it still triggers ghost touches a bit too early for my taste, especially when pressing petal 8 with a thumb (which is the natural way to reach it when holding the flow3r in left hand). As mentioned earlier, it's a band-aid to get rid of an annoying 1.3.0 regression - it's still not hard to get ghost touches when you press two top petals firmly with two thumbs for example, but bumping the threshold even higher doesn't seem like a viable solution.
It doesn't appear to be a noticeable issue for bottom petals, so I left those unchanged.