test: increase coverage of internal/stream/end-of-stream

This change adds test cases to call the function returned by
end-of-stream and asserts that callbacks are not called when
the stream is ended, or prematurely closed.

PR-URL: #23751
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-stream-finished.js

@@ -119,3 +119,25 @@ const { promisify } = require('util');
   rs.push(null);
   rs.resume();
 }
+
+// Test that calling returned function removes listeners
+{
+  const ws = new Writable({
+    write(data, env, cb) {
+      cb();
+    }
+  });
+  const removeListener = finished(ws, common.mustNotCall());
+  removeListener();
+  ws.end();
+}
+
+{
+  const rs = new Readable();
+  const removeListeners = finished(rs, common.mustNotCall());
+  removeListeners();
+
+  rs.emit('close');
+  rs.push(null);
+  rs.resume();
+}