test: use default assertion message

In test-child-process-spawnsync, the assert.strictEqual() custom
message was hiding information about why the test has failed. It
just showed what value is expected and in case of failure we want to
know which value has caused test to fail.

PR-URL: nodejs#16819
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/parallel/test-child-process-spawnsync.js

@@ -28,7 +28,7 @@ const spawnSync = require('child_process').spawnSync;
 // Echo does different things on Windows and Unix, but in both cases, it does
 // more-or-less nothing if there are no parameters
 const ret = spawnSync('sleep', ['0']);
-assert.strictEqual(ret.status, 0, 'exit status should be zero');
+assert.strictEqual(ret.status, 0);
 
 // Error test when command does not exist
 const ret_err = spawnSync('command_does_not_exist', ['bar']).error;