test: improve assertion in process test

PR-URL: #22634
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/parallel/test-process-env-allowed-flags.js

@@ -50,7 +50,7 @@ require('../common');
 // assert all "canonical" flags begin with dash(es)
 {
   process.allowedNodeEnvironmentFlags.forEach((flag) => {
-    assert.strictEqual(/^--?[a-z8_-]+$/.test(flag), true);
+    assert(/^--?[a-z8_-]+$/.test(flag), `Unexpected format for flag ${flag}`);
   });
 }