test: remove custom error message

Default error message contains the actual and expected values,
which is more informative than the custom error message to be deleted.

PR-URL: #19526
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Shingo Inoue <leko.noor@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-fs-readfilesync-pipe-large.js

@@ -28,8 +28,8 @@ const node = JSON.stringify(process.execPath);
 const cmd = `cat ${filename} | ${node} ${f} child`;
 exec(cmd, { maxBuffer: 1000000 }, function(err, stdout, stderr) {
   assert.ifError(err);
-  assert.strictEqual(stdout, dataExpected, 'it reads the file and outputs it');
-  assert.strictEqual(stderr, '', 'it does not write to stderr');
+  assert.strictEqual(stdout, dataExpected);
+  assert.strictEqual(stderr, '');
   console.log('ok');
 });