test: show incorrect value on test failure

PR-URL: nodejs#16818
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Khaidi Chu <i@2333.moe>

Author: Sean Karson

test/async-hooks/test-promise.promise-before-init-hooks.js

@@ -16,7 +16,7 @@ hooks.enable();
 p.then(function afterresolution(val) {
   assert.strictEqual(val, 5);
   const as = hooks.activitiesOfTypes('PROMISE');
-  assert.strictEqual(as.length, 1, 'one activity');
+  assert.strictEqual(as.length, 1);
   checkInvocations(as[0], { init: 1, before: 1 },
                    'after resolution child promise');
   return val;