refactor(library/data/subtype): elaborator does not need help anymore (i.e., 'show'-expression) for this file

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(library/data/list): avoid placeholders '_', make first argument of false_elim implicit

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(library/data/list): avoid placeholders '_', make first argument of false_elim implicit