fixup! prevent drawing separators on starting lines of fields

On non-consecutive ranges, we were drawing the starting line _on top_ of
the separator, which lead to some visual glitches in some viewers.

src/renderer.typ

@@ -392,6 +392,7 @@
     range-boundaries.push(start-i)
     range-boundaries.push(end-i)
   }
+  range-boundaries = range-boundaries.dedup()
 
   // Draw colors
   for i in range(struct.bits) {