any_of markdown output is misleading if each set only has one member

[Oberon00]

E.g. see https://github.com/open-telemetry/opentelemetry-specification/blob/v1.0.1/specification/trace/semantic_conventions/database.md#connection-level-attributes

Additional attribute requirements: At least one of the following sets of attributes is required:

• net.peer.name
• net.peer.ip

Obviously the set here is {"net.peer.name", "net.peer.ip"}, so you need both. Except: This is wrong! There are two sets, one contains only net.peer.name and the other only net.peer.ip.

I think if each set contains only one member, the text above the list MUST change to "At least one of the following ~~sets of~~ attributes is required:" (without the ~~sets of~~).

[thisthat]

I am not a native speaker, so I cannot judge properly which is the best phrase to use here. Would you also remove "sets of" in the case where multiple attributes are listed? An example of this is in the HTTP Client semantic convention:

Additional attribute requirements: At least one of the following sets of attributes is required:

• http.url
• http.scheme, http.host, http.target
• http.scheme, net.peer.name, net.peer.port, http.target
• http.scheme, net.peer.ip, net.peer.port, http.target

[Oberon00]

I think if at least one set has more than one member, the current phrasing is clear and in these cases I would keep it as-is.

[lmolkova]

Related: #293

[lmolkova]

Closing this since we no longer support constraints - 310