Update API Version to supported Netbox Version (3.1.3)

[liquid-metal]

Hello,

for my purposes I wanted to work with ASNs in this provider but I noticed them not being present. During investigation I noticed that referenced go-netbox library (https://github.com/fbreckle/go-netbox) is generated for an ealier version (3.0) which does not include the API entpoints I need.

In my opinion it is reasonable to use the API version of Netbox that is "officially" supported by the current provider release.

I create a PR in the go-netbox repo with the updated files: fbreckle/go-netbox#9

Please let me know if I can contribute any further work to get the current API version to work.

[fbreckle]

I completely agree and recently merged the 3.2.0 client in fbreckle/go-netbox.

Note that Netbox 3.2.0 contained breaking changes in sites with regard to ASNs.