fix: remove .json suffix from entity requests

[jaark]

Netbox 4.1 throws an error if '.json' is appended to API requests. Previous versions silently ignored this deviation from the published API spec. This change corrects the requests for entities.

eg.
GET /api/ipam/ip-addresses/1/

instead of
GET /api/ipam/ip-addresses/1.json

Fixes #89

[thde]

Thank you for the PR! The specs URL's will also need to be adjusted for them to succeed. For example:

netbox-client-ruby/spec/netbox_client_ruby/api/ipam/rir_spec.rb

Line 12 in 6246a45

let(:request_url) { "#{base_url}#{entity_id}.json" }

[jaark]

Sorry, I didn't notice the spec tests. They should be fixed now.
But... I am still seeing a single failure. I'm not sure where that is. I don't think it has anything to do with my changes as I get the same issue from the main tree, It looks like it might be something to do with the version of faraday here.