test: Use strictEqual in test-tls-writewrap-leak

PR-URL: nodejs#9666
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-tls-writewrap-leak.js

@@ -20,7 +20,7 @@ const server = net.createServer(common.mustCall((c) => {
   });
 
   c.write('hello', common.mustCall((err) => {
-    assert.equal(err.code, 'ECANCELED');
+    assert.strictEqual(err.code, 'ECANCELED');
     server.close();
   }));
 }));