Update qhelp example to more accurately demonstrate flagged cases

javascript/ql/src/Quality/examples/UnhandledStreamPipe.js

@@ -2,5 +2,7 @@ const fs = require('fs');
 const source = fs.createReadStream('source.txt');
 const destination = fs.createWriteStream('destination.txt');
 
-// Bad: No error handling
-source.pipe(destination);
+// Bad: Only destination has error handling, source errors are unhandled
+source.pipe(destination).on('error', (err) => {
+  console.error('Destination error:', err);
+});