test: remove string literal arg from assertion

Remove unnecessary string literal from assert.deepStrictEqual() call.

Backport-PR-URL: #22912
PR-URL: #22849
Reviewed-By: Teddy Katz <teddy.katz@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: Trott

test/parallel/test-fs-readfile.js

@@ -54,6 +54,6 @@ for (const e of fileInfo) {
   fs.readFile(e.name, common.mustCall((err, buf) => {
     console.log(`Validating readFile on file ${e.name} of length ${e.len}`);
     assert.ifError(err);
-    assert.deepStrictEqual(buf, e.contents, 'Incorrect file contents');
+    assert.deepStrictEqual(buf, e.contents);
   }));
 }