Revert "ping: switch to async style"

This was causing crashes =/

damus/Nostr/WebSocket.swift

@@ -45,16 +45,8 @@ final class WebSocket: NSObject, URLSessionWebSocketDelegate {
         self.session = session
     }
     
-    func ping() async throws -> () {
-        return try await withCheckedThrowingContinuation { cont in
-            self.webSocketTask.sendPing { err in
-                if let err {
-                    cont.resume(throwing: err)
-                } else {
-                    cont.resume(returning: ())
-                }
-            }
-        }
+    func ping(receiveHandler: @escaping (Error?) -> Void) {
+        self.webSocketTask.sendPing(pongReceiveHandler: receiveHandler)
     }
     
     func connect() {