test: better output for test-report-uv-handles.js

PR-URL: #27479
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/report/test-report-uv-handles.js

@@ -85,7 +85,7 @@ if (process.argv[2] === 'child') {
   const report_msg = 'Report files were written: unexpectedly';
   child.stdout.on('data', (chunk) => { stdout += chunk; });
   child.on('exit', common.mustCall((code, signal) => {
-    assert.deepStrictEqual(code, 0, 'Process exited unexpectedly with code' +
+    assert.deepStrictEqual(code, 0, 'Process exited unexpectedly with code: ' +
                            `${code}`);
     assert.deepStrictEqual(signal, null, 'Process should have exited cleanly,' +
                             ` but did not: ${signal}`);