test: replacing assert message with template

PR-URL: #15974
Reviewed-By: Ruben Bridgewater <[email protected]>

Author: Barry Tam

test/parallel/test-cluster-disconnect-suicide-race.js

@@ -8,7 +8,7 @@ const cluster = require('cluster');
 
 if (cluster.isMaster) {
   cluster.on('exit', (worker, code) => {
-    assert.strictEqual(code, 0, 'worker exited with error');
+    assert.strictEqual(code, 0, `worker exited with code: ${code}, expected 0`);
   });
 
   return cluster.fork();