test: remove string literal from assertion

Remove string literal from `assert.strictEqual()` call `message`
parameter and make it a comment above the assertion instead.

Backport-PR-URL: #22888
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>

test/parallel/test-next-tick-domain.js

@@ -27,5 +27,5 @@ const origNextTick = process.nextTick;
 
 require('domain');
 
-assert.strictEqual(origNextTick, process.nextTick,
-                   'Requiring domain should not change nextTick');
+// Requiring domain should not change nextTick.
+assert.strictEqual(origNextTick, process.nextTick);