fix possibility for infinite signaling on read

Author: tanner0101

Sources/TCP/Streams/TCPSocketSource.swift

@@ -142,13 +142,9 @@ public final class TCPSocketSource: Async.OutputStream {
     /// Called when the read source signals.
     private func readSourceSignal(isCancelled: Bool) {
         DEBUG("TCPSocketSource.readSourceSignal(\(isCancelled))")
-        guard !isCancelled else {
+        if !isCancelled {
             // source is cancelled, we will never receive signals again
             cancelIsPending = true
-            if downstreamIsReady {
-                readData()
-            }
-            return
         }
 
         guard downstreamIsReady else {