test: changed assert.equal to assert.strictEqual

PR-URL: #10015
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

test/parallel/test-child-process-stdio-big-write-end.js

@@ -23,7 +23,7 @@ function parent() {
     n += c;
   });
   child.stdout.on('end', function() {
-    assert.equal(+n, sent);
+    assert.strictEqual(+n, sent);
     console.log('ok');
   });