NIM: Clarify support for 24.04 tech spec guide

[mjang]

          24.04 isn't in the tech spec guide -- should it be added?

https://docs.nginx.com/nginx-instance-manager/fundamentals/tech-specs/#supported-distributions

Originally posted by @travisamartin in #142 (comment)

[mjang]

Question, @mkingst : For what version of NIM do we support Ubuntu 24.04? We'll add it to the last line of this table (as shown from the link)