http: simplify sending header

unshifting into an empty array is the same
as creating a new array.

PR-URL: #33200
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Zeyu Yang <himself65@outlook.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

lib/_http_outgoing.js

@@ -289,19 +289,11 @@ OutgoingMessage.prototype._send = function _send(data, encoding, callback) {
       data = this._header + data;
     } else {
       const header = this._header;
-      if (this.outputData.length === 0) {
-        this.outputData = [{
-          data: header,
-          encoding: 'latin1',
-          callback: null
-        }];
-      } else {
-        this.outputData.unshift({
-          data: header,
-          encoding: 'latin1',
-          callback: null
-        });
-      }
+      this.outputData.unshift({
+        data: header,
+        encoding: 'latin1',
+        callback: null
+      });
       this.outputSize += header.length;
       this._onPendingData(header.length);
     }