Make GRPCStatusAndTrailers `Sendable` (#2204)

Adds a `Sendable` annotation to `GRPCStatusAndTrailers` in v1

Co-authored-by: George Barnett <gbarnett@apple.com>

Sources/GRPC/GRPCStatusAndMetadata.swift

@@ -18,7 +18,7 @@ import NIOHTTP1
 
 /// A simple struct holding a ``GRPCStatus`` and optionally trailers in the form of
 /// `HPACKHeaders`.
-public struct GRPCStatusAndTrailers: Equatable {
+public struct GRPCStatusAndTrailers: Equatable, Sendable {
   /// The status.
   public var status: GRPCStatus