Update API specs to consistently use Key Set

[lmilan]

The Admin API specs use Key-set and the Konnect API uses KeySet, these should be updated to use Key Set everywhere

[Guaris]

I was going to do this but I think it requires a bit of discussion. In Konnect it's KeySet, the admin API schema is using key-set. I think the specs should reflect the schemas, so we might want to wait for auto generation for this one.

[lena-larionova]

Use Key Set everywhere to follow the Konnect UI.

[Guaris]

Kong/docs.konghq.com#8393

[Guaris]

Kong/kong#14234