http: remove redundant condition

`conn.destroyed` is guaranteed to be `false` because a previous `if`
statement already handles the case where `conn && conn.destroyed`
evaluates to `true` returning `false` in that case.

PR-URL: #29078
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

lib/_http_outgoing.js

@@ -285,7 +285,7 @@ function _writeRaw(data, encoding, callback) {
     encoding = null;
   }
 
-  if (conn && conn._httpMessage === this && conn.writable && !conn.destroyed) {
+  if (conn && conn._httpMessage === this && conn.writable) {
     // There might be pending data in the this.output buffer.
     if (this.outputData.length) {
       this._flushOutput(conn);