bindings: rust: libgpiod: release 0.2.1

bindings: rust: libgpiod: release 0.2.1

While the release technically removes a function, that function was not
available in any released libgpiod version. Therefore, this only bumps
the minor.

This release fixes building with releases from the 2.x series of the C
lib.

Changelog:
=========

acebcf2 (bindings: rust: feature gate unreleased features, 2023-10-06)

Signed-off-by: Erik Schilling <erik.schilling@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>