Remove unused import Dispatch from Message.swift (swiftlang#1156)

This import is unused and is redundant in that file

Author: MaxDesiatov

Sources/LanguageServerProtocol/Message.swift

@@ -10,8 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-import Dispatch
-
 public protocol MessageType: Codable, Sendable {}
 
 /// `RequestType` with no associated type or same-type requirements. Most users should prefer