[python][generator] Use the alias that is already defined
In the generated code there will be a typedef
created that is marked with DUNE_UNUSED
because it is unused.
This MR improves readability of the generated code and makes DUNE_UNUSED
obsolete at the same time.
- changes the typedef to an alias
- uses the alias in the actual
insertClass
class - removes the now obsolete
dune/common/unused.hh
include