python unwinder doc improvement

Paulo Neves via Gdb-patches
2022-05-28T11:56:17Z

[PATCH 1/2] gdb/python doc: Add register_unwinder to code example
[PATCH 2/2] gdb/python doc: Add enable property to the unwinder

Minor documentation changes to the unwinder example code with the goal
of having all the features described in the prose also reflect on the
code.