[6.0] Fix API docs errors

[smitpatel]

Resolves #23260

[smitpatel]

@Pilchie - XML doc only change.

[Pilchie]

👍🏻

[roji]

@smitpatel is there some document somewhere explaining the prefixes (e.g. O vs. M)? I remember we discussed this at some point but am not sure I know what to use when...

[ajcvickers]

Thanks for doing this, @smitpatel. Great to get XML docs updated before they are published for 6.0.

[smitpatel]

@roji https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/xmldoc/#id-strings
here is list of all IDs. "O:" is missing. I have filed a doc issue to update docs.