Use single guillemots on L4 (not less/greater) where L3 has guillemots

The latin/basic layout has less/greater signs on layer 4 where layer 3 has (double) guillemots, i.e. AB01 and AB02. Presumably the less/greater signs are an error and what was really intended were the single guillemots, as the less/greater signs are already available on layer 2. This presumed error has also been replicated into a bunch of layouts derived from the Latin one: double guillemots are routinely paired with the less/greater signs, which are even more readily available on layer 1 and/or 2.

This MR replaces the less/greater signs on layer 4 with single guillemots where layer 3 has double guillemots.