`ref` modifier appears to be removed from `struct` types

[BillWagner]

See more details in dotnet/docs#5208

There are couple important points here:

• For types (like Span<T>) that are ref struct types, the ref modifier is missing.
• When a method signature returns a ref T, the ref T modifier is missing.

[BillWagner]

A similar problem happens for ref readonly struct declarations.

[joelmartinez]

For the second point, that will be addressed in the next release by the resolution to #249

[mairaw]

@joelmartinez should I add a new issue or just include the conditions from MicrosoftDocs/feedback#468 here too given this one is still open?

[joelmartinez]

@mairaw Yeah, a new issue would be ideal, so we can keep the scope of each issue a bit more focused. This one will be for the ref struct, and the new one will address the indexer ref scenario

[mairaw]

OK, filed a new one for the indexers then: #422