notepat: remove orphaned m4l download rail from top bar
The rail was drawn at y=0 backing osBtn/abletonBtn when they lived in
the top bar, but those buttons moved into the OS_BAR row in b279bead5.
The leftover decoration floated behind wave/octave, creating a visible
teal rectangle under the octave button.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>