Bumps [github.com/alecthomas/kingpin](https://github.com/alecthomas/kingpin) from
v2.2.6 to v2.3.2.
This also changes the upstream package name from
gopkg.in/alecthomas/kingpin.v2 to github.com/alecthomas/kingpin/v2 which
is required by the upstream exporter-toolkit package.
Signed-off-by: Ben Reedy <breed808@breed808.com>