Fix bottom scanline not reaching the bottom edge

Changed SCANLINE_SKIP from (12,28) to (8,20) -- the old set dropped
position 28, the one closest to the bottom edge, leaving a gap there.

subwave_nowplaying.star

@@ -558,7 +558,7 @@ def _glitch_scanlines():
     # positions instead of the last two in the run -- which left an 8px
     # gap with nothing in it at the bottom of every cycle -- spreads the
     # resulting two, slightly-larger gaps across the full height instead.
-    SCANLINE_SKIP = (12, 28)
+    SCANLINE_SKIP = (8, 20)  # keeps a line at y=28, near the bottom edge
     tall = ART_SLOT + SCANLINE_PERIOD
     lines = []
     for y in range(tall):