[CS0420][Fix] `Mailbox`

[eaba]

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[eaba]

We should probably remove the Volatile.Read call - since the field is already volatile. @Aaronontheweb

[Aaronontheweb]

We should probably remove the Volatile.Read call - since the field is already volatile. @Aaronontheweb

Complicated issue from a semantics point of view, but I wonder if we should do this the other way around in order to guarantee atomicity https://github.com/dotnet/runtime/issues/67330#issuecomment-1083106423