stream: avoid writing to writable

A remainder from a previous refactoring.

Refs: nodejs#31197

Author: ronag

lib/_stream_writable.js

@@ -687,7 +687,6 @@ function endWritable(stream, state, cb) {
       onFinished(stream, state, cb);
   }
   state.ended = true;
-  stream.writable = false;
 }
 
 function onCorkedFinish(corkReq, state, err) {
@@ -741,7 +740,7 @@ ObjectDefineProperties(Writable.prototype, {
     get() {
       const w = this._writableState;
       if (!w) return false;
-      if (w.writable !== undefined) return w.writable;
+      if (w.writable !== undefined) return w.writable && !w.ended;
       return Boolean(!w.destroyed && !w.errored && !w.ending);
     },
     set(val) {