prometheus-wireguard-exporter: 3.1.1 -> 3.2.0

https://github.com/MindFlavor/prometheus_wireguard_exporter/releases/tag/3.2.0

Previously, the exporter used `wg show all dump` by default to retrieve
information about wireguard peers. If a wireguard config is set, the interface is
now extracted automatically and the exporter runs `wg show <interface> dump`[1].

The cargo hash didn't change as no dependency updates were done in this
release.

[1] https://github.com/MindFlavor/prometheus_wireguard_exporter/pull/17/commits/4e332cb73ffafea8ae37ecf12da68602f4a8a049